I added my friend as an administrator, to my blog. He changed permissions, locked me out, and now I don't have access. Can Blogger get my blog back?Here, we have bad news for you.
The only way you can prove ownership of a blog is from having control. If you give up control of your blog, it becomes somebody else's blog.
If you want control of the blog restored to you, this becomes an internal dispute between you (the former owner), and your previous friend (the current owner).
Blogger Support can't involve themselves in internal disputes.
Once again, we have to remind you to only give control of your blog, to people you can trust.