There's a chance he wasn't dead, that's how they hibernate, in frogs its called estivation.
Estivation is the term given to the period of Hibernation that wild African Bull Frogs usually go into during the dryer months. They create a cocoon from old skin that helps to seal in moisture whilst the frog buries itself in the ground to wait for the rainy season to come
http://www.theamphibian.co.uk/Africa..._adspersus.htm