The problem with your argument, Max, is that if they WERE declassified, it is not a crime for those people to have them. In fact, it's not a crime for YOU to have them. So if there is to be an indictment, it has to be over documents that are, in fact, classified. Well, sort of. A good prosecutor can indict a ham sandwich and all that, and, of course, a DC jury would without question exonerate a Democrat and nail a Republican to the wall, particularly if we are talking Trump.
We also have no idea what happened with the Biden documents any more than we know what happened with the Trump ones. But the Trump ones would require the complicity of the Secret Service, who were responsible for the secure location, and the Biden ones would require the complicity of Hunter, or Jim, or Joe's cleaning lady, or Joe's pool boy, or even the cleaning staff at the Penn Biden Center. Those locations never were secured.
Not how it works, None. Back when I had very limited access, I was patted down both before and after, as well as watched by a pair of security guards. While if we were talking about mid-level bureaucrats or especially military, missing documents would all get intensive investigations, including probably midnight raids and possible anal probes, they do not do that to Senators or other important people. It's just logged, and if it's deemed important enough, might get investigated.