for what it's worth, I worked with a rather high end junior organization last year, and we had some people DQ'd after leaving the roped off scoring area without signing (some who even seemed not to have signed on purpose), and then there were some instances of cheating that we did not find out about until that evening or the next day. So as not to distract the other members in the cheater's group, we didn't DQ the player until after their round they were set to play. Fortunately, a rules official was always in the scoring area and any unsigned scorecards were reported that day, usually at that moment.
I do think it's odd that no one of enough importance was in the scorer's tent of an LPGA event to notice that Michelle Wie had left the area without signing it as it happened.