MongoDB shell version: 2.0.1
connecting to: localhost:27018/offerStore
mongos> db.offer.count({shopId: 205640});
166031
mongos> var count = 0;
mongos> var cursor = db.offer.find({shopId: 205640}).batchSize(1000);
mongos> while(cursor.hasNext()){cursor.next(); count++;}
2317
mongos> db.offer.find({shopId: 205640}).batchSize(1000).explain()
Mon Jan  9 14:46:09 uncaught exception: error: {
        "$err" : "could not initialize cursor across all shards because : no
ts field in query @ offerStoreDE2/s197:27018,s209:27018,s198:27018 ::
and :: no ts field in query @ offerStoreDE3/
s117:27018,s129:27018,s118:27018 :: and :: no ts field in query @
offerstore/s142:27018,s144:27018,s143:27018",
        "code" : 14827
}

mongos> db.offer.count({shopId: 205640});
166031

Here are the router logs (level 6):
http://pastebin.com/raw.php?i=UbUBdTqf