This reminds me of what happened to me in WoW. Back in WotLK or BC I think, maybe it was further back, I played a rogue on alliance side and had made a friends with a pally. We started raiding together and I would lead a lot of pug raids that went rather successfully since I would look for people a few days before, screen them, etc. Too much time spent on that honestly, was easier just getting into a good guild and being part of their runs.
Anyway, pally and I were together for a long while and eventually I quit. We lost contact eventually.
Then comes cataclysm and I decide to start playing again, nothing serious. I start a goblin mage and thought I'd just play for the storyline and crap... nope. I powerleveled my !@# to 85. I got there pretty quick, in about 2 weeks.
Eventually, joined a good guild and raided, was the top guild in a very populated (one of the original) servers, actually, progression wise anyway. Unfortunately drama happened and the guild split up.
I started looking around for guilds, but I wasn't satisfied with being with low progressed guilds.
Anyway, one day I saw a name that I recalled, or at least it was similar, but when I /who'd the person, it was a different class and I recall he was alliance.
Eventually, I saw a similar name again, and who'd it and saw it was a pally... so I whispered him. Turns out it was him. And he had faction transferred with a small band of people I remembered raiding with. Unfortunately, they didn't care for progression as much as I did, though they were doing decently. He was being cocky saying that they could do it... but progression doesn't lie. I was into heroic raids already and they had just finished the normals.
But still, since I had nowhere to go, caught up with each other a bit. Was good memoriess and talking to him again.