I was wondering if anyone could give me a hand.

I've been having vague memories of a fic I read quite probably years back now. 

The only things I remember are Xander working construction on the outskirts of SunnyD after the big bang to rebuild it (or excavate it I'm not sure which), finding Spike in the rubble and something about a church in the rubble? I think Spike hid something in it, or that's where they found him? 

I know it's not much to go on but if anyone has any ideas I'd be grateful.