You are not going to get the parts back Dana.
He probably knew the parts were gone (whether he took them or not)... and was probably hoping to find another 'junk' ped and take parts off it to replace the ones that were missing from yours... but he never found one.
So you got screwed.
If you could find him.
And if you are mad enough about it... you could demand the approximate amount of cash to buy the parts used.
Or sell the ped to him for its value before parts were taken.
But you (and others) now know not to leave anything in his (or his friends) care.
Or let anybody hold something of yours without working on it.
Just take it back the minute you think something is fishy.