ETA: Ok, I also gave up on finding the other fic that I was looking for. This one I remember a bit more about though, so yay! It had Xander trying to protect Spike, and so their captured by the initiative, and they bond (vampire bond) they manage to escape, but one of them (Xander?) manages to get caught again (Riley?) and the Scoobies try to rescue him, but only manage with the help of Dru.