The likelihood of the rom going bad from the drive from one location to another is very low.

Without the piggy deux board plugged in, it's just not going to boot the game since that's where the gamerom is.

Getting a test rom for system 80 would be helpful and troubleshooting on the bench with a power supply instead of in the game where other factors might mask what's going on. Even without a test rom, testing on the bench with a logic probe/scope is helpful. You're going from the assumption that it was working when you picked it up, something has changed.

Inspect the board closely for any possible battery damage, too. Think about what go disconnected (if anything) for the ride.... did you take any of the connectors off/take the head off? (I forget if that's a fold-down head on that game). Some games just don't like to be moved, connectors are the top choice for issues there. While a connector doesn't just one second to the next go from good to bad, there could be bad spots on the connector or the edge finger and moving the game just causes it to stop making contact.