It Wasn't Obvious Enough
One of the players gets his character sheet back after having someone else play for him when missing the previous week. He scans it front and back to look for the tell-tale changes that indicate he's missing several limbs, has some interesting new diseases, or has beneficently bought everyone in the party a magical weapon from his gold reserves. We were somehow on our best behaviour as none of this had happened. One thing seemed to be missing from his sheet that he expected to see, however. 'Where has the XP gained from the last session been written down?', he asks, after checking all over the sheet.
'Uh, in the XP box.'
And he plays a character with high wisdom.