He lands in rock. It is horribly uncomfortable and crushes the experimental worldleaper and would definitely be fatal if he weren't indestructible but he is so he just tries to teleport home.
It doesn't go.
He tries teleporting a million miles from here in an arbitrary direction, because he can figure out from there what's wrong about going home.
...he is still in rock.
What the -
He tries again, and again, and again, squishing and bruising himself as far as he can be squished and bruised every time, and then he concludes that it looks like he has found a dimension that is entirely made of rock and should go home only he can't go home -
- he teleports all the rock around him to somewhere a million miles away. Okay. He does that several times until he has a reasonable amount of space.
Now he can curl up and cry, so he does that, and he teleports rock away while he does. And puts in some air and some furnishings and makes it a pretty rock cave that he apparently can't get out of, because that's easy and sort of reassuring.
He tries again to go home. It doesn't work. Maybe this dimension prohibits a teleport out?
It's technically risky but doing it once isn't too risky ...he makes a worldleaper, jumps. Lands in vacuum, like normal. He beams at the vacuum. Vacuum is lovely. So much better than infinite rock. And can he teleport back to his rock cave?
...he can. And from his rock cave to the world with vacuum, and back - okay, so the problem isn't that this dimension prohibits a teleport out -
- the problem could be that he's not adjacent to Warp. Jumped twice, somehow, while playing around with the prototype worldleaper.
He wants to light everything on fire. He makes gasoline everywhere in his rock cave and makes a match and strikes it and the cave doesn't even turn into an awesome fire because there's no air.
He scowls and makes the cave bigger and does it again. Now everything is on fire. He feels better.
It is a day later when he conjures for complete written works of endless-rock-universe's Bell.