I left my viewer running overnight and when I woke up the sim had apparently reset (nothing weird here right?). I logged back on to realize that a LOT of objects on my parcel had been returned, and my parcel prim count had been maxed out -- without anybody having placed anything new, it seems. I've used Area Search and the Land tool to try and see if there were any new objects floating around (there apparently were none) and now I'm in the process of checking whether or not my items were messed with in ways that might have increased their land impact. Also a few items have different collision now than they did before, specifically where I had left my avatar idling overnight (in this case, shoving me away from areas I was formerly able to walk in. I'm still troubleshooting that one and trying to figure out which object is suddenly screwy).
I have no idea what happened as I don't know anybody who would have targetted me for something I did or didn't do -- it seems like a drive-by thing simply for idling with my fiancee, or alternately the sim my land is in had its prim limit scaled back without warning. I haven't edited my parcel for about a week, but since my objects got a bit wonky for no reason, it may have been a hacked client that allowed them to spoof identity or my avatar was commandeered somehow -- or as I said, prim limits in my sim got nerfed without warning.
Does anybody have an idea as to what happened?