I'm sure a film would be very helpful...
To make if clear for you though... assists don't give any points (I'm assuming you're talking about perk points).
As for the kill, most likely it was a proxy kill. Basically a plane crashed near you and you got the 'credit' for the kill. In these cases, no perk points are awarded either.
If you DID in fact land hits on the P47 before it lost a critical part of itself, then this is indeed a bug... however, if the P47 happened to clip a tree, ripping off its right wing and while it was going down you landed hits on it, then it would still be a proxy kill (hits landed on a 'doomed' aircraft do not count).
But yeah, without a film it is simply speculation.