I typed in wrong email on fb, then tried to log in.Can they tell it was me for certain

Possibly with a keystroke logger. This would not be automatically installed (they're illegal, I believe).

You are probably fine, but do your best to be more careful. One or two errors like that can be explained away as simple mistakes. Many more than that and you really will look like a stalker. As for where that line is drawn, I'm sure no one knows.