I know what you mean. It's one of the strangest things I've seen.
I know the Web Dev. who upkeeps and maintains the content of the site had to do a recovery (File & Database recovery) because they crashed the wordpress and it was unrecoverable. I could definitely see some kind of tomfoolery happening because of this process.
I called GoDaddy before creating this thread to work through this with them, and was escalated. They told me they thought it was cacheing, and that they didn't see anything server side either.
Find searches in all directories and sub-directories from where you start. If you want to start in the directory you're currently in, you use a period. (I.e find . -name "*.pdf")
Also, it's not in any of the *.zip files -- I've checked.