Deleted META-INF file in Minecraft- Help!?

So I downloaded a mod, and eventually went back and deleted every file I put in there, but I pretty much completely deleted the meta-inf file, which I need to connect to my brother's server. (it's his account I was in) and I don't know his password, it's 'remembered' or whatever. So if someone could link me a download to a normal .minecraft file, that would be amazing. If not, could someone tell me how to download the meta-inf file without reinstalling the game at all?