Thankfully we've not had too much damage, but every time it was something we found and no one told us about. That really makes me angry...especially if it is a stain, it's always easier to get it out the sooner you find it. We've never charged for anything like this even though we were tempted to.
The worst one we had was a couple with their adult mentally challenged son all staying in the same room. One queen bed and one twin bed, we thought the son was staying on the twin but evidently he was in the queen and he soaked everything with urine not once but twice. The first day they just left it all there for us...what a disgusting mess and the smell was unbelievable. We had to replace everything on the spot because they were staying over that night, luckily it all laundered ok. The next morning they had replaced our sheets, mattress pad and blanket with new ones from the local store, and left the comforter off the bed. But they still never said anything, they snuck out early.