It's not that unlikely
I can easily believe that 10% of passports lost are lost by young people on nights out.
Most people need to take their passport outside their home maybe 3 or 4 times a year. A lot of young people who don't have a driving licence take it out at least once a week so there's much more opportunity to lose it.
Or (as happened to me a few years ago) have it stolen from a nightclub cloakroom.