> That doesn't work here because the data was not wiped by a generic cache flush from a third party script or whatever

But it was, it was program other than vim (neovim) that did it. It deleted a file in a space that is meant for transient files that may be deleted at any time for any given reason and should not cause data loss, and yet it did because vim, in the first place, broke the file system’s contract.

Neovim shouldn’t have been messing there but at the same time there’s a much bigger culprit here in that vim shouldn’t have been storing this kind of data there in the first place. It was a broken system that broke even further. Simple as that.