Yikes! At least you caught it before it drained completely.
I agree - if you can transfer the substrate, decorations and the filter as well as some of the water, you're really just performing a big water change, so I see no harm in adding him as soon as the temperature is good. You might want to keep an eye on ammonia and nitrite levels though, since you might lose a decent amount of bacteria during the tank change.
Good luck, and let us know how it goes!