A couple of Saturdays ago, I was on I-17 near Bell Road, when I spotted about 12-14 Vipers of every form and color parked at the Martin Auto Museum. Obviously a club run, but a very impressive impromptu display.
Not likely. Odds are it would have been recovered long before now if it was on the streets. Typically, these cars that remain at large for years are hidden away, usually by a "private collector."