So it was visited and reported with data like the main star, then later purged from EDSM after you downloaded your data? I wonder what criteria EDSM uses to purge data, did that happen when they moved everything to the new servers I wonder, because there was a bit of hold up there, would have been a huge task at the time and they might have been trying to minimise the amount of data they were moving around.
EDSM was doing it for a few months before the move to the new server. Anthor was trying to prevent the server from completely running out of space. Eventually he did that server move, and and was able to stop purging data, but quite a bit was already purged at that point. Also, during the server move there were a few days where EDSM was down and not receiving data, so I probably have some data from those days via EDDN that never even made it into EDSM at all. That would be a small amount though. The vast majority of the "missing" data on the EDSM side is just due to the purging, and it's still a small minority of the data compared to the whole.
Ok done, a carrier jump with a CMDR on board will record the stars and asteroid belts and a first visited tag to EDSM, so systems with no data can't be attributed to FC's, an empty FC won't report any data, and a CMDR on board will record at least the main star and a first visited tag!
Right, these would have to be one of two things-- systems that were merely jonked in the pre-FSS days (system exists in the data, but no body data submitted), or cases where EDSM purged the body data, but not the system. I was under the impression that it would all have been purged, but maybe it was just the bodies, since that's where the bulk of the data storage footprint is located. I wouldn't be surprised if EDSM prioritized keeping the systems even if it was purging the bodies.