Level 1-1 in the normal ending, a ladder appears when time is going backwards.
look at 4:05 on the left side. 
http://www.youtube.com/watch?v=shYKscyW2LA&feature=fvw

I cant reach it, so its maybe just a bug?

If it's the same thing I'm thinking, when I played it through I wasn't even sure if that ladder was even there when going forward. It might the game again just filling in as it's stopping him from getting to her, going forward that lever would have been to let you past, but in reverse it'd have done nothing, and not aided in stopping you from getting to her in anyway, so they added a ladder.
 
Does that make sense?
Am I even thinking the right thing.

i have played now again through the last level, and there are many such ladders. I've must been tired to not see them. So they have no sense in the game, there are just symbolic.