If you're really far in it might take some searching...oh! And if you find a stream of water, that might lead you out, too! I remember something about underground streams forming caves over time as they find their way to the surface.

[Those teeth aren't nearly so off-putting to Alphonse as they might be to others--he's used to Wrath and Greed, after all. And the fire lighting on Rin's fingers makes Al grin as well.] Oh wow, that's so cool! I can move earth and air with alchemy, but I never figured out fire.