I agree with Chuck, after all this time you are going to have a hard time proving anything.
The guy who took it apart will just say it was all there when he gave it to your friend, and if that is what he says you will not have a leg to stand on.
It was up to your friend to prove it was all there when he took it off this guy, if he did not do any sort of check then that is probably the end of the story.
Why has it taken you this long to raise the subject?
You needed to do it a year ago, not now.