Not below freezing now, still have to wait a few minutes. It will eventually move over to the right side so you can pull it down into reverse,

 

I know this is a stretch, but have you tried a hair dryer? Even if the temp would barely dip below freezing overnight, my Mom would put a hair dryer under the hood of our old Ford, right on the distributor cap to warm it up and dry it out. Possibly heat the shift mechanism? Of course this sort of assumes you're in a garage where an outlet is handy. Moisture and cold can do funny things to plastic parts. Good luck