On a slab foundation, what happens to the old plumbing pipes when the kitchen is moved to another room?

A previous owner built an addition to the house we live in now - a one-story with a slab foundation. The addition is a large kitchen, and the room that obviously was the old kitchen is now kind of a bedroom/den located in between the new kitchen and living room. It seems like it would be much better to have the kitchen in its old room next to the living room, and have the addition part of the house be a large back porch-type area or bedroom. So my question is, is it likely that the old pipes where the kitchen sink used to be (under a small window) are still there and usable? Or would the plumbers have somehow taken them out or done something to make them impossible to reuse? It wouldn't be worth digging up the slab to lay a new pipe, but if the old pipe was still there, it seems like it would be feasible to move the kitchen sink and cabinets back to their original room.