Most likely the person riding this bike around the city and taking the time to lock it up doesn’t know it's stolen.
Probably purchased it from the crack head that originally stole it, or from some sleazy pimp that’s passed it around like a dirty whore.
I'd be prepared for a some conflict and suggest Properly registering it when you do get it back. So you'll have recorded proof of owner ship this time.
Oh Ya be sure to ware gloves with this girl now maybe even two as you don't know who's done what kind of nasty sexual things to it and what kind of VD you might pick up.
Dam Moped Sex Trade!!!