Pick up the stone

As you reach down for the stone, a cold wind snakes through the cavern, chilling the bones in your arm. It passes quickly, and you grab the stone, holding it in your fingers initially before allowing it to fall down into your palm.

The instant it does so, there's a bright, blinding flash and an instant of intense cold in your hand, followed by intense heat, and then nothing. You hear a clatter of the rock falling to the ground, slipping out of your hand as you lost the concentration to hold on to it, its light gone out. There's no way to tell what happened, your only immediate indication being a sense of being cold, and something... else, that you can't quite identify yet.

When you feel a strange fabric brush against your skin in your groin area, you realize what's different- somehow, the rock's flash magically removed the underwear that you were wearing. Your clothes weren't affected, just undergarments, and in the dark you have no idea where they could be. There's still enough light to see, somehow, and you can make out the distinct outline of an exit in the wall where you saw a change earlier.