US Chess member id 12678873 is not present in either MSA, MUIR, or the recent all ratings TSV file:
…but they have recorded tournaments?
In MUIR they’re just missing for that tournament, but that doesn’t really seem to be MUIR’s fault for a change.
I know of 504 IDs that were in the previous crosstable system but not in the membership system because those IDs were purged in the 80’s and 90’s. (I think 2 or 3 of them are in deleted events, so the actual count on MUIR is a little lower.)
Unfortunately we have no digital records that would contain those IDs. That’s one of the reasons I’ve been pressing for digitizing 40+ years worth of printed rating supplements and posting them, because that way we might be able to use an OCR tool to recover those records digitally and maybe find some of those lost members.
We have found a few over the years, I think George Mirijanian found one because it was an opponent in one of his tournaments. And I think I found another that belonged to a GM who died in the mid 80’s. But the new membership system has no way to restore purged IDs, so if we ever do find out who any of those people are, we’ll probably have to give them IDs that start with a 3.
I thought the plan was to create faux accounts on MUIR for those IDs, but maybe that got lost somewhere along the way.