Kind of bumping this because, I too seem to have gone around all there is to do in the temple and am apparently completely unable to leave.
Got a bunch of upgrades. Bumped into the boss that says it’s Patreon only. Went down into the water area with no mini-map where apparently a boss was moved away from…. The two possibilities that I can find are next to each other, in the big shaft outside the patreon-only boss, but both are one-tile gaps high up in the air.
Only place I wasn’t able to explore was the area to the left of the “main room” in the temple (the one that opens up to allow access into the water section) as that place seemed to be locked
EDIT:
Started a new game and a lot of things made sense now. And yes, I was indeed soft-locked inside the temple.
Upon starting the game, I saw the ladder leading up to all of the collectibles and was like “oh.. all right then. Sure, in development” and picked everything up. This allowed me to essentially sequence-break into the temple through the top entrance, by sliding in.
The rooms I mentioned, to the left of the temple’s main room are, in fact, the main entrance and it can only be opened from the outside. It also happens to be the only accessible way out which put me out of luck.
Maybe for the next preview build it would be helpful to add a tag explaining the collectibles on the start room and maybe regardless of this nonsense, a couple of buttons to open up the temple from the inside would be a good idea in general, just in case someone manages to do the same thing of coming in through the top.