My 2 cents...
If they didn't read the rules, they they have already broken them. No excuses, no way out.
It clearly states in the rules what not to do. So either they knowingly disobeyed the rules, or disregarded them. NOW with that having been said...
Some people do validly make mistakes. I know 1 person who miscounted the squares to vend by 1. An honest mistake that anyone can make. But you know what? He won't make that mistake ever again!
The point of maintaining a punishment and not letting anyone slide is two-fold. First, it teaches those who didn't mean to do something to pay more attention. Secondly, if anyone gets to slide with an excuse, EVERYONE jailed will say "I didn't see *reason*" or something similar.