I have a TSAURO-X buggy from Radio Shack (60-4117). The car was not used for a couple years and unfortunately the batteries in the remote leaked. I was able to clean up the contacts (ex-Navy electrician), but the wire from the negative battery terminal (connected to the springs inside the battery terminal) and and the circuit board completely fell away. I can resolder a new wire to the battery compartment contact, but have no idea where it connects to the circuit board.

Would anyone know where it attaches?

Most of the time the larger copper surfaces and metal shieldings on the PCB are the ground. You can doubble check that if the negative of the larger capacitors on the PCB are connected to the surface.