I bet I know where I picked it up then. I remember passing shreds of truck tire treads coming back to Illinois on the Clark Bridge. All the crud from everywhere seems to drift right into the bicycle lanes on the Clark Bridge, including at least two pieces of lumber and a fist-sized wad of bailing wire.
Edit: Yes, I think that IS a bullet-hole in the upper right hand corner of the Bike Lane sign... Missouri is overrated. I'll stick to the IL side from now on...