To be "in the shop" means that one is
recovering from a particularly brutal hangover. Usually seen lying on the bed, couch, floor, etc. covered head to toe with a blanket. Similar to putting your car in the shop for a
tuneup, but your body (especially your
liver) is getting the tuneup.
Todd:
Hey Kevin, where's Rob? He was pretty drunk last night.
Kevin: I dunno, last I saw him he was lying on the couch covered completely in a
blanket.
Todd: Oh, he must be in the shop.