The scene was in Bargaining, while Spike was looking after Dawn after Buffy's death.
It was a wonderful scene, but Marti clearly thought we liked it too much, so she decided to not give us any more of them
(out of an idea that it might make people ship them, which I totally cannot understand!! There was nothing shippery in that scene, not between them anyhow. If anything, it only strengtened my spuffy-love)