So here were many of the guesses as to the culprit of the blotch.
1. Got into mom's lipstick
2. Lipstick from a lady's kiss
3. Mailbox crash
4. Bike Fall
5. Twin cherry popsicle
6. Sidewalk crash
7. Screen Door crash
8. Tree crash
9. Rug Burn
10. Cat Scratch
11. Brother Scratch
12.Red Tie Dress (not really a guess, but it was a funny comment)
13. I loved the idea of magic marker to erase it
In actuality, it happened at church.
The real story actually isn't terribly interesting, really. On Sundays after church, I teach several piano lessons in the choir room. While I was teaching, Aaron came in and I noticed the blotch. He, of course, couldn't tell me where it came from. It wasn't until a half hour later as we were FINALLY leaving church that Steve told me what had happened.
Apparently, Aaron decided to see if he could balance ON TOP of a ball. Imagine his surprise that the ball did indeed roll out from under him, plummeting him into the cement floor of fellowship hall. Steve assures me that he was right there when it happened, Aaron didn't cry a bit, and that it looked "much worse" before he cleaned it up.
It looks much better now but it was just so painful looking that whole day.