Wow, that is a really good question that "Bob" has.
If "Bob" has never been charged of a legal crime, regardless when and who and how often he had sex with his girlfriend at the time, then it isn't really a crime. And it isn't lying.
If this guy at the place "Bob" was applying thought he was lying about this it may be worth bringing it to a lawyer or at least talking to one. You would have to prove things like that is the reason you were disqualified for the job, and that the person in charge new about "Bob" prior relationship and how in his mind must have been illegal or something.
I'd go find a lawyer and talk with them. Most lawyers I think offer a free consolations.






