I once went to Le Mans on my uncles passport. Didn't spot it on the way out (on a coach, mass hand in of passports)
On the way back they checked it on the ferry, it was about 3am monday morning, you had to go to passport control, and by that time i looked a bit 2nd hand. The bloke behind the desk loked at the passport then at me, gave me the passport back with no problem.
Probably frightened him!