diff --git a/CloudObjects/SDK/ObjectRetriever.php b/CloudObjects/SDK/ObjectRetriever.php
index 6df451a..ee41b9e 100644
--- a/CloudObjects/SDK/ObjectRetriever.php
+++ b/CloudObjects/SDK/ObjectRetriever.php
@@ -680,9 +680,30 @@ class ObjectRetriever implements CustomCacheAndLogInterface {
 				$this->putIntoCache($cacheId, $fileData, 0);
 
 				$this->logInfoWithTime('Fetched attachment <'.$filename.'> for <'.$object->getId().'> from Core API ['.$response->getStatusCode().'].', $ts);
+			} catch (ConnectException $e) {
+				// connection failed or timed out
+				$this->logInfoWithTime('Attachment <'.$filename.'> for <'.$object->getId().'> could not be retrieved from Core API (connection failed).', $ts);
+				throw new CoreAPIException($e->getMessage(), $e);
+			} catch (RequestException $e) {
+				if ($e->hasResponse() && $e->getResponse()->getStatusCode() == 404) {
+					// not found (404)
+					$this->logInfoWithTime('Attachment <'.$filename.'> for <'.$object->getId().'> not found in Core API.', $ts);
+					return null;
+				} else
+				if ($e->hasResponse()) {
+					// other API error (4xx, 5xx)
+					$statusCode = $e->getResponse()->getStatusCode();
+					$this->logInfoWithTime('Attachment <'.$filename.'> for <'.$object->getId().'> could not be retrieved from Core API ['.$statusCode.'].', $ts);
+					throw new CoreAPIException($e->getMessage(), $e);
+				} else {
+					// API error without response
+					$this->logInfoWithTime('Attachment <'.$filename.'> for <'.$object->getId().'> could not be retrieved from Core API (no status code).', $ts);
+					throw new CoreAPIException($e->getMessage(), $e);
+				}
 			} catch (Exception $e) {
-				$this->logInfoWithTime('Attachment <'.$filename.'> for <'.$object->getId().'> not found in Core API ['.$e->getResponse()->getStatusCode().'].', $ts);
-				// ignore exception - treat as non-existing file
+				// other exceptions
+				$this->logInfoWithTime('Attachment <'.$filename.'> for <'.$object->getId().'> could not be retrieved from Core API (unexpected exception).', $ts);
+				throw new CoreAPIException($e->getMessage(), $e);
 			}
 
 		}
diff --git a/tests/OfflineTests/ObjectRetrieverMockTest.php b/tests/OfflineTests/ObjectRetrieverMockTest.php
index 1abe406..6601616 100644
--- a/tests/OfflineTests/ObjectRetrieverMockTest.php
+++ b/tests/OfflineTests/ObjectRetrieverMockTest.php
@@ -115,6 +115,35 @@ class ObjectRetrieverMockTest extends \PHPUnit\Framework\TestCase {
         $this->assertNull($content);
     }
 
+    public function testWhenAPIThrowsErrorForAttachment() {
+        $this->setMockResponse(
+            new Response(200, ['Content-Type' => 'application/ld+json'],
+                '{"@id":"coid://cloudobjects.io/Test","coid://cloudobjects.io/isAtRevision":"1-abc"}'),
+            new Response(500)
+        );
+
+        $this->expectException(CoreAPIException::class);
+        $this->retriever->getAttachment(new IRI('coid://cloudobjects.io/Test'), 'file.txt');
+    }
+
+    public function testWhenAPITimesOutForAttachment() {
+        $this->setMockResponse(
+            new Response(200, ['Content-Type' => 'application/ld+json'],
+                '{"@id":"coid://cloudobjects.io/Test","coid://cloudobjects.io/isAtRevision":"1-abc"}'),
+            new ConnectException(
+                'cURL error 28: Operation timed out',
+                new Request('GET', 'cloudobjects.io')
+            )
+        );
+
+        try {
+            $this->retriever->getAttachment(new IRI('coid://cloudobjects.io/Test'), 'file.txt');
+            $this->fail('Expected CoreAPIException was not thrown.');
+        } catch (CoreAPIException $e) {
+            $this->assertInstanceOf(ConnectException::class, $e->getPrevious());
+        }
+    }
+
     private function createFallbackStoreDirectory() : string {
         $directory = sys_get_temp_dir().DIRECTORY_SEPARATOR.'clobj-fallback-'.uniqid();
         mkdir($directory);
diff --git a/tests/OnlineTests/ObjectRetrieverCacheTest.php b/tests/OnlineTests/ObjectRetrieverCacheTest.php
index 63564ad..c52911d 100644
--- a/tests/OnlineTests/ObjectRetrieverCacheTest.php
+++ b/tests/OnlineTests/ObjectRetrieverCacheTest.php
@@ -51,4 +51,34 @@ class ObjectRetrieverCacheTest extends \PHPUnit\Framework\TestCase {
         $this->assertEquals($object2->getRevision(), $object3->getRevision());
     }
 
+    public function testAttachmentCacheInRuntimeStorage() {
+        $cacheStorage = new VolatileRuntimeStorage;
+        $logger = new InMemoryLogger;
+
+        $coid = new IRI('coid://cloudobjects.io/Test');
+        $cacheId = (string)$coid.'#file.txt';
+
+        $retriever = new ObjectRetriever([
+            'cache_storage' => $cacheStorage,
+            'logger' => $logger
+        ]);
+
+        $content1 = $retriever->getAttachment($coid, 'file.txt');
+
+        $this->assertEquals('Test file content', trim($content1));
+        $this->assertNotNull($cacheStorage->fetch($retriever->getCacheKey($cacheId)));
+        $this->assertStringContainsString('from Core API', $logger->getLastLogMessage());
+
+        // Reinitialize retriever with same cache storage to verify that cache is used
+        $retriever = new ObjectRetriever([
+            'cache_storage' => $cacheStorage,
+            'logger' => $logger
+        ]);
+
+        $content2 = $retriever->getAttachment($coid, 'file.txt');
+
+        $this->assertEquals('Test file content', trim($content2));
+        $this->assertStringContainsString('from object cache', $logger->getLastLogMessage());
+    }
+
 }
diff --git a/tests/OnlineTests/ObjectRetrieverPublicTest.php b/tests/OnlineTests/ObjectRetrieverPublicTest.php
index 7aa38e5..0f54b47 100644
--- a/tests/OnlineTests/ObjectRetrieverPublicTest.php
+++ b/tests/OnlineTests/ObjectRetrieverPublicTest.php
@@ -33,6 +33,15 @@ class ObjectRetrieverPublicTest extends \PHPUnit\Framework\TestCase {
         $this->assertEquals('CloudObjects', $object->getProperty('http://www.w3.org/2000/01/rdf-schema#label')->getValue());        
     }
 
+    public function testGetTestObject() {
+        $coid = new IRI('coid://cloudobjects.io/Test');
+        $object = $this->retriever->getObjectNode($coid);
+        $this->assertNotNull($object);
+        $this->assertEquals((string)$coid, $object->getId());
+        $this->assertNotNull($object->getProperty('http://www.w3.org/2000/01/rdf-schema#label'));
+        $this->assertEquals('Test Object', $object->getProperty('http://www.w3.org/2000/01/rdf-schema#label')->getValue());
+    }
+
     public function testGetRelatedObject() {
         $coid = new IRI('coid://cloudobjects.io');
         $object = $this->retriever->getCloudObject($coid);