My Library folder is missing. What do I do?

I just noticed that my Library folder is missing from my home folder. I have the one on my hard drive but not in the home folder. I did a search for it and cannot find it. I went into Time Machine and found it way back in November of 2011....it did not show up after that. It was about that time when I installed Lion...maybe in that process I lost it from my home folder.

If I can't find the missing one....and I can't.....should I restore the old one in Time Machine? I started to do that but then I got the question about do I want to have it REPLACE the old one (I don't know where the old one is to replace), do I want to save BOTH files, or do I just want to leave the old one. I would leave the old one if I knew where it was but I don't. What should I do.....should I check 'replace the old one?" Then the library folder will be one from 2011. Does that matter? I don't want to do the wrong thing. Please advise.

Thank you so much.