Animals have a great tendancy to repopulate suitable habitat, if given have a chance. I don't doubt for a minute that captive cougars have been set free by unprepared pet owners. I don't know if they'd have the ability to survive long, but they would probably be seen on occassion.

I recently read an interesting study where they had done some gene profiling on the Eastern Coyote. They found that it contained a percentage of wolf genes, but no dog genes. It appears that it is a wolf hybrid (small percentage of wolf), not a coydog.