From talking to people and having witnessed this happen to others on the bus. No worries, they'll give you a warning before it happens, and they wont ever strand you there by taking away your return ticket (not like they can take it from you). All they can do you give you talk at the service counter, then ban you from getting onto the bus for next time.
Guys, it's the same damn PAC card you get onto the bus with, that you put into the slot machines. Of course they have a detailed record of what you're gambling there. How else do they upgrade you from blue to gold then platinum if they weren't tracking you?