Be sure to familiarize yourself
Hearthstones are waterproof, but are not lava or magma proof. For the latter - chances are - that neither are you, so this should not cause any real concern.
In the case that you misplace or lose your hearthstone, most Innkeepers are stocked with a supply of replacement stones and pouches, at no cost to you. However, as a wise man may or may not have once said, Jade Dynasty Gold can be costly enough. Be sure to familiarize yourself with the proximity and location of any Inns in your adventuring area.