rob,
You’re right, the source I found was a typo, it’s actually 2:3, and not so clear in what way the heavenly bodies differ from the things we find here on Earth, but apparently, it’s normally understood to mean that they are not solid enough to land on. On YU’s Torah site, there’s a lecture from R’ Nosson Kamenetzky in which he supposedly relates the story with his father zt”l (although I didn’t listen to it), and it may have been recounted in Yonoson Rosenblum’s R’ Yaakov biography, although I don’t have it in front of me and I don’t remember it with certainty. I do remember that Rosenblum got much of his information from R’ Nosson.