No offense to other Trek owners. You guys are cool. Kind of. (pic via Reddit)
When did bike thievery get so complicated? You have people tracking down their bikes on Craigslist and stealing them back. Others rescuing their stolen bikes and leaving cardboard cutouts in their place. Now there are thieves who are basically pretending they're in some kind of grassroots bike share program to assuage their guilt?
Saddest thing would be if this Trek belonged to a bystander who witnessed the theft, and was so personally affronted by it that he wanted to do a good deed to make up for the crime. So he walked into the garage and left the victim his own bike. He'd rather be bikeless, and know he did good by someone in need than ride away knowing some poor biker had been victimized.
Then he'd wander back the next day and find his bike, with this note attached, and a slow tear would roll down his cheek. He just wanted to fight the bad with some good.
But nah, it was probably just an asshole who stole this bike, then found a better one to steal so he dumped this in its place.