Did you sign a work order by chance? Did they ask you to sign anything before doing the work? If not, your word against theirs. Small claims court for the price of the items you expected to get back. If you did sign a work order, read thru the fine print. You may or may not have a case. Most people don't want the old parts back. But, unless you left it there for a few days, I doubt anything was hauled off. Good luck either way.