Unfortunately they've already been wiped, the difference between your PST and your other office documents is that when you save a word document it sticks it in a common folder (my documents, or whatever you tell it to) where the excel PST file is actually more of a system file than a document. It's default location is inside the outlook directory and because of that is vulnerable to being deleted with outlook.
If there are no PST files on your hard drive it's been deleted, you can look up the default personal file location for your version of outlook and see if it might be there in a different format, but probably not. I think your only option to recover it would be to use data recovery software and look for files with the .pst extension. I wouldn't be optimistic about this process considering you over-wrote a lot of data in the recovery process.