Lock retaining clip lost in door?

Alright gang so we have a success story here - solid idea with the camera.

The clip ended up indeed being INSIDE the support beam box and was a real pain to get out.  We ended up using one of those cameras and a long piece of thick gauge wire to keep poking at it until it peeked its head out for a quick grab with the tweezers.

I'm happy to report no more rattles and door locks that are usable now haha.

Thanks for all your solid ideas per usual!