Leaf Scorch on Japanese Mapel
If drought shock is the cause, the plant may simply be in forced, early dormancy. This is a physiological survival response. I would not discard the plant yet. Keep the root system moist. You will have to be careful not to overwater since little water use is now occurring. Keep the tree until next spring. It may leaf out again and come out of dormancy. If no leaves appear by May/June, I think you can assume recovery will not occur.
If you suspect that excess salts are the problem, you should repot your maple tree. Unpot the tree, wash most of the old soil off the roots and then repot with new potting soil.