I'm sure it can happen but I'm sure those instances were years ago? Possibly back before all the witch hunts started with UC pets? Things really only got bad when people started reporting random pets and sending tickets in to check on the "legitimacy" of certain pets. It went downhill from there very quickly.
I remember back in the day trading active UCs for other pets and getting away with it. Things like that would never fly today because everybody is so up in everybody elses business haha