beat the game but didn't get the achivement?

[Remicon]

So... I beat the game last night and was really proud of that, but I couldn't help but notice that the achievement on steam didn't pop like it was supposed to. Any idea why? All I could were people saying the achievement locks itself if you switch to a save that's before you beat the game, but I haven't done that. I know one person somewhere (i think it was on gamefaqs?) said you could just launch the game with a post TLB save loaded up and it would unlock, but that didn't work either for me, I even played through to 2-4 a second time on the beaten save just to make sure and nothing happened.

If anyone has any other ideas on how to fix it that'd be great.

[Remicon]

...Nevermind. I opened the game up again and for some reason, the achievement popped THIS time. Don't know if it was a bug or what that it didn't go off last night. So i guess if it happens to anyone in the future, try playing through the game a little bit more and then close and open it again?