No small number of pilots have been fired or unable to gain further employment over the years as a result of clandestine operations that exploit the cozy relationships between airline management staff. This is perhaps truer of Asian airlines than European ones, ("leaving the family" is a great sin in those cultures) Singapore and EVA pilots having a particularly difficult time.
Anyone who's reputation has been contaminated by this sort of practice has my heart-felt sympathy, proof is indeed hard to come by and the hardship is a terrible one. I'm surprised the caretakers of our present legal system have not yet realized the potentially enormous payouts involved.
Seems you can check out of this hotel, but you can never leave.