diff --git a/pandora_client/__init__.py b/pandora_client/__init__.py
index 97d00e1..01e13e0 100755
--- a/pandora_client/__init__.py
+++ b/pandora_client/__init__.py
@@ -808,20 +808,21 @@ class Client(object):
                 o = 0
                 chunk = 5000
                 while o < n:
-                    files += self.api.findMedia({
+                    files += [f for f in self.api.findMedia({
                         'query': query,
                         'keys': ['item', 'id', 'extension'],
                         'range': [o, o+chunk]
-                    })['data']['items']
+                    })['data']['items'] if f['extension'] in DOCUMENT_FORMATS]
                     o += chunk
-        d = []
+        documents = []
         o = 0
-        while o < len(files):
-            d += self.api.findDocuments({
+        ids = list(set(f['id'] for f in files))
+        while o < len(ids):
+            documents += self.api.findDocuments({
                 'query': {
                     'conditions': [
-                        {'key': 'oshash', 'operator': '==', 'value': f['id']}
-                        for f in files[o:o+chunk]
+                        {'key': 'oshash', 'operator': '==', 'value': id}
+                        for id in ids[o:o+chunk]
                     ],
                     'operator': '|'
                 },
@@ -829,10 +830,9 @@ class Client(object):
                 'range': [0, chunk]
             })['data']['items']
             o += chunk
-        available = set(f['oshash']
-                        for f in d if f['extension'] in DOCUMENT_FORMATS)
-        missing = [(f['id'], f['item']) for f in files
-                   if f['id'] not in available and f['extension'] in DOCUMENT_FORMATS]
+        available = set(f['oshash'] for f in documents)
+        missing = [(f['id'], f['item']) for f in files if f['id'] not in available]
+        missing = list(set(missing))
         return missing
 
     def find_document(self, oshash):
@@ -867,7 +867,7 @@ class Client(object):
                 'id': did,
                 'item': item
             })
-        return True
+        return did
 
     def upload_document(self, args):
         if not self.user: