If you filled out the 4473 in full, signed it,,,and the NICS check was completed (with a 'Proceed' given),,BUT,,the firearm is not physically transfered at that time (waiting period,ect),,then the buyer has to re-sign the 4473 and date it again in a separate section further into the form when it is picked up from the FFL.
If the FFL has the 4473 filled out, but the transaction is not followed through to the point of a NICS check being called in and a NICS check # is never issued to the FFL for the transfer,,then the 4473 form for that xfer can be destroyed by the FFL. It does not have to be kept.
IF the NICS check was called in and a # issued by the FBI for that transaction (there's a place for it on the 4473),,then that 4473 has to be preserved and kept by the FFL no matter if the transaction is followed through with or not.
It has to also be kept if there is a DENY response, or a Delay and in the latter if the xfer is never completed.
The way the FFL/Pawn dealer pulled the gun transaction from under the OP would make me feel uneasy at the least about having made out that 4473 and having them tell me 'we never called it in'. All that after going through the FLA waiting period. Why wait to call it in when they could have run up against a DENY response from the FBI 10 days ago. Then put the rifle right back up for sale then.
I too would call the local BATF office and explain the situation. They have a Compliance Office that handles such things and these are the Agents that pay visits to the FFL's to check their records and inventory to make sure things are run on the up & up.
They've seen about every trick in the book to side step transfer paperwork and do backdoor deals.
It might not be the first time anyone has called about the Shop.
Either the FFl's books will reflex the correct situation with the rifle, that it was simply sold to another person. (Quite possible & just plain poor business practices for them.)
There may be a 4473 on file in the OP's name w/a NICS check done but 'No Transfer Completed" written and signitured/dated on it in their records, ( I doubt it..)
,or a 4473 w/a NICS check done with the OP's name on it for that rifle, the rifle gone from the books as sold to the OP and a Pawn Dealer/FFL with a lot of explaining to do. (Could be,,and that would bother me..a lot)
jmo