I once turned a valuable counter-weighted Corvette crankshaft into a machine shop for re-grinding, and they tried to give me a non-counterweighted Chevy crank when it came to pick it up.  When I insisted, they located my crank.
  I also had a friend turn in some rare early VW parts to a plating shop for re-chroming, and many of them were 'lost', never to be returned.
  Another friend of mine had a restoration shop charge very big bucks to completely re-do his early Karmann Ghia convertible, and they 'lost' the riveted VIN tag, affecting the resale value greatly.
  I recommend getting a signed receipt, an itemized list and mark your parts, maybe even using hidden stampings, engraving, digital pictures or such, to protect you from loss or theft by unscrupulous shops.  This is the only way to have your case stand up in court, if that becomes necessary, later.

Mike B.