I am currently on Level 0 (this part looks like the fungal caves) and have explored all I could, killed enemies, found 3 Masks of the Golden God (lol wut?) but have yet to find any way out. No doors, no teleporter, no boss, nothing. Um, what now? :c
Try walking on tiles obstructed by the camera. I find half the time it is on a tile blocked from view by a wall and I can faintly see the grey edge of the teleport tile.
FINALLY found it. Eesh. Um, maybe teleporters should get the nice red "here I am" outline that revealed traps get when obscured by walls/objects.
Since this question gets asked about three times a month, Tycho's idea seems very good to me. I've also wandered over displacement glyphs because they were hidden by overhangs, so maybe we could do this for all teleport tiles?