And this was spread across all times of the day, not just one particular login period - I had several interactions with the guy and then suddenly his regular login times asploded, and never saw him again.

One of my characters also had the locate object spell, and when I was bored, I would spam it repeatedly checking for a lot of the best gear. I mean, he still logged on periodically I suppose, in order to keep his equipment for this long, but they would have to be pretty short and sparse login times if I never saw him again.

Shrug. I login a lot less now, being kept busy by moving and classes, but a set like that is very distinctive and hard to miss. I really doubt two chars would be able to gather a nearly identical set within such a short time period and then lose it to anti-hoarding code.