Don't worry, you didn't lock yourself out. It's a minor oversight on my part, but the entrance doesn't become visible on the map after you discover it, however it's still interactable (I'll make sure it changes visually in future updates).I went to the first temple, failed to beat the fire genie, and left. I updated to this last version from the previous one and now I can't find the entrance to the temple. I speak with the old dude in the magi guild library and he tells me he doesn't know other temple locations. In the town market, the person the sells maps only talk but I don't get an option to buy any maps so I can't find a way into the temple that way neither. Did if soft lock my progress with the temples/shapeshifting?
Exit Tarkas and go straight west, the entrance to the temple is right there, in the mountains. Also, the fire genie has a trick to it, it's not a straightforward fight. I hope this is enough to guide you in the right direction.