I never thought of Promanea as a garden plant for zone 4 . Just teasing - I once froze a Odm bictoniense rock solid, left it overnight in a car when outside the car it was -10 F (about -23 C) - the car stayed a bit warmer than outside - the pot and potting mix were frozen solid, lost all the leaves and psuedobulbs, but about 2 months later, new shoots came up from the rhizome. It took 5 or 6 years to recover, but I have bloomed it again.
The reziliance of orchids amazes me.
A "vague but true" recollection, I think you will have a better chance of getting regrowth after a freeze from Neotropical species over old world species.