Found along the canal path.
Theory A: Too far gone to hear the kickstand fall off the bike, or to care about it.
Theory B: Far too cool to ride one single foot farther sporting a kickstand.
Theory C: Across the flowing water, on the other bank, he spotted the love of his life, and nothing could stop him getting over to her before she rode away, not heat, or greed, or distraction, or fear, or doubt, or indifference, or indecision, or parts falling off his prized bicycle.
Theory D: A proud exemplar of our throwaway society suddenly found he had no further need of a kickstand for reasons other than style, and discarded it in place. Perhaps, for example, he never figured out what it was for, or how it worked, assumed it was broken, and time to get a new one.
Theory E: Someone placed it there in my path to test my reaction.
Theory F: It's not actually a kickstand, it's something else, and I am terribly mistaken.
Get up. Go ride.