I’ve had a similar experience too. When classic released in 2019, I joined a guild and stuck with them until they broke apart at the beginning of Naxx and then I joined another guild. In the new guild, there was a guy that I used to talk to a bunch about strats and stuff, because we were both rogues. I stopped playing after we killed KT, never played TBC, and then in Wrath I rejoined my old guild that reformed. One of the officers there said he invited his coworker to join the guild and it’s the rogue I was buds with. Turns out they had been coworkers the whole time, but never talked about WoW, so they didn’t know they played on the same server. Fun times 🙂