I'll just add a couple of questions to Carlos' great advice:
Does the shriveled up hand look like a fresh wound?
Roughly how long is the frog from the tip of it's nose to it's rear?
ps. Gray Treefrogs were once sometimes referred to as "Tree Toads". So if it is a Gray, you aren't far off in your thinking. They have dryish, bumpy skin that is typical of a toad.