The only story I can think of with Buffy in a coma is The Body by Spikesheart. But I think that was set around S4, I don't think I have read the one you're describing, but I'd like to of course!

.
The one I was thinking of all I remember about it was that when Buffy found out she had been given some money she assumed it was from Angel and rushed off to ring him and obviously he didn't know what she was talking about. I don't remember any other events/context for that one unfortunately do it is probably a stretch for someone to remember the scene.