I think we can theorize on what happened with Snow. When Lightning disappeared he went "I'm a hero and I'll find her!" and went to find her. He probably got lost. And ended up like this. Then Serah took this as a "he doesn't love me!" thing, and the story starts. Only that he does love her, so depending on how we go on with the story, she'll believe him or she'll just get with Noel.
Something like that anyway.
Waddya think?
PS: gonna watch the trailer.
EDIT: Ha! So he did go after Lightning! That's one part of my prediction come true
By the way, Snow doesn't look like a creeper, he seems to be having difficulties to stand on both feet and is leaning on Serah. And by the little Japanese I understand, when Noel accuses him on not protecting Serah, he states it's fine, because he was there to protect her.
And I think at the last bit Lightning said something about protecting the future, but I'm not really sure.