Splitting /usr and using an empty partition

[cwalke32477]

My /usr is showing 81% full, which means it is time to do something.
I have an old /var partition that was removed, after it became full, and symbolic link, created by the DC, moved /var elsewhere.

Well now my /usr is nearing capacity. I have a lost partition that has about 10gb of free space on it that I feel could be utilized by /usr, since it no longer houses /var.

My questions:
1. How do I locate the lost partition? the /var path, that was using it, was deleted from the command line, when it was moved. (stupid me)
2. How can I move half on my /usr there?
3. How does symbolic linking work?

Any advice would be appreciated.