There is always the chance a war vet or another similar individual will need a single shoe.
I had this happen - I knowingly picked up a Florsheim shell beacuse it was an unusual model. It was like a dollar for the one shoe... they had it mated with some obvious wrong shoe. I had them look and offered a reward for the other shoe, but nothing doing. I planned to sell it just as that - one shoe - but I'm not sure if i still have it or if I got tired of it kicking around and chucked it