I don't remember much, buffy and spike lived in a cave? Spike went missing for a bit, or possibly buffy. I think Lloyd the demon that gave spike his soul back made an appearance...or I'm confusing it with another fic.

I believe it was set after btvs finale, could have also possibly been a time travel fic? Haha

thank you in advance!

I found this topic:
Post AtS, Spike and Buffy lost in the caves the fic was 'We Own The Night', by OKDeanna. It was published in 2009 but it has been taken down.
Summary:
Canon, Post Series Buffy Summers hated lying, but sometimes a girl had to do what a girl had to do and this, unfortunately, was one of those times. Because if she told Spike the truth, he'd likely think her insane, but if she lied, if she said she was happy for him when she wasn't, maybe he'd come to realize what she'd only just begun to learn.

Maybe 'All Our Yesterdays' by Evenstar I haven't read it yet but I took a pick and apparently they seek refuge in caves.

    Summary: The First Evil was not defeated, but as time passed it seems it also did not vanquish the Earth. Now, in a post-Apocalyptic world only three Scoobies remain and are following a Slayer's dream to possible salvation. Post-Season 7 A/U.

That's all I could find for the moment. I'll keep looking. 😉

Hannora
Omg it could be all our yesterdays! I'll check today and get back to you! Thank you!!