Well, those are stored on your computer (my default is at C:\Program Files\City of Heroes\PowerCust). See if it's there. If not, I'm not sure there is a way to get it back other than just redoing it. Assuming same AT and powerset choices, right (Is it plugged in and turned on? 
)?
EDIT: Apparently I'm blind and totally missed that you said it's there already. 
I've had some of mine not save properly before, but not commonly.
Dec out.
I was making a new character and saved a powercust file (I see it in my folder) to work on it more later, but when I try to load it up again, it's not listed by the game. How can I get it to load? Is this a common issue?