Buffy and Spike undercover as bf/gf or husband/wife

disclaimer: tried searching - I promise!

Buffy and Spike are undercover as bf/gf or husband/wife. I remember specifically one scene in which they're in a hotel room that's bugged and spike can tell something's wrong with buffy and she says one thing out loud while trying to keep it together, but writes something else down on a piece of paper and gives it to him- maybe that her mom had died?

sorry if this is vague. I think it's from a long time ago.

Is this an AU fic, or are they still Vamp and Slayer?

b_loves_s
Could it be "Smoldering Ice" by William's Girl?

Link:

Smoldering Ice by William's Girl

http://www.sinister-attraction.net/stories/w/smoldering_ice.htm

Summary: Special Agent, William Barrows and finds himself on assignment in Brazil. Sent there on a rescue mission to find his former partner he becomes caught in a web of memories. As past and present timelines converge truths are revealed, sacrifices are made, passions ignite, and he discovers his capacity for love.

Guess we have a winner, so I'm moving this to FOUND!!