Found: Left Teva size 9 Gnarkosi
Maybe a longshot, but.....
I have been looking at this lonely shoe at the Eben G. Fine park put-in for the last week. Come claim it at the Colorado Water Sports 3600 Arapahoe Ave, Boulder,CO location. Your right shoe is missing it's buddy.
"Huck Finn?...more like huck-and-swim"