Leon was certain of just one thing; the lizard transported him into that world, knowing that he would have a hard time going back. Still, even though that monster has the power to travel between worlds and slow down time, his powers weren't absolute. Otherwise, he wouldn't need to use humans or interfere with Leon's work.
"If the humans of this world can use magic… then they faced the same problems we faced. I bet I can find some dungeons in this world, and using those will be the easiest way to return home."
The problem was, Leon could end up getting even more lost. Besides, he was pretty sure he didn't hear of a dungeon that spawned humans that had stones on their foreheads. So the chance of him finding a dungeon that would lead him directly to Earth was null.
