I went into app settings and under google there was an allow or disallow for downloads. It was in one of your old posts. I tried it and it worked like a poster mentioned.
That sounds like Storage permission for the Google app.
I just tried to reproduce what you've been dealing with, and I was mostly successful, except for that fact that I could actually delete the file. This is what I did (again, on a Pixel 3 XL):
1. Turned off Storage permission for the Google app in
Settings>Apps.
2. Opened the Google app (not Chrome) and searched for a small sample PDF -- downloaded it.
3. Looked for the file -- it's not in the main user download directory (i.e., /storage/emulated/0/Download). The only way I can find it is if I use the native stock file manager app on the Pixel 3 XL, called "Files" (which is different from Files by Google, which can be installed from the Play Store).
4. If I use the Files app and go to the Downloads category (note that I say "category," and not "directory"), I see the sample PDF file there. However, if I go to the user-accessible /storage/emulated/0/Download directory, it's not there. I can't find that file in any other user-accessible directory -- the only way I can see it is in the stock Files app's Downloads category.
5. So far, I think we're on the same page. The difference, though, is that I see the file as being a few Kb in size (it's a small PDF), and I can delete it using the stock Files app.
6. If I turn Storage permission back on for the Google app and re-download that PDF, it shows up in the user-accessible /storage/emulated/0/Download directory now.
So what I think happened was that you downloaded that file at some point using the Google app when the Google app didn't have Storage permission, and so the file went to a download directory that might only be seen by the stock file manager app. I'm not sure why you're unable to delete the file using the stock file manager, though.
Remind me -- what happens if you use your stock file manager app (presumably My Files) and look in the Downloads category? Is the file there? If so, what happens if you long-press it?