Thermal stone new skin still bugs sometimes, sometimes when going in caves or when you loging out and later back in.
Also if you use thermal stone skin and put thermal in ice box, wait till it will be freezing cold and thermal stone will have normal skin.
Equiping it, it still does not change the skin back, only when you drop it on ground, but picking up it again, it still will be no skin.
Skin will only change back when its not freezing cold anymore.
Put thermal stone in ice box and wait till its freezing cold