I've noticed that it sometimes goes to the first available hotbar slot, rather than the one I designated for it, after use. Haven't had it vanish, though.
I wonder if it would make sense to ditch the winch item entirely, and make it a button in the UI window for the vehicle wagon.
Oh, I have a minor bug report: when winching/unwinching a tank, the currently selected weapon is reset (to the cannon), and with the Vehicle Equipment Grid
mod, the vehicle's "Enable logistics while moving" setting is reset as well.