Since I've not yet been able to open 2009, technically there isn't a "last" workspace. I tried removing each of the available workspaces one by one just in case though, but that hasn't worked.
I don't know if this is useful, but I still have 12.5 installed. From what I've read in other topics, this shouldn't be a problem, but if this gives anyone some ideas, I'd be happy to try them out.