I'd only been away less than 24 hours. We're completely shocked, and terribly sad.
Calli had been rescued as a semi-feral kitten back in 1998. She was very affectionate, and followed us around the house, protesting with her high pitched mew if she saw us leaving the safety of the house. She'd done outside, and inside was so much nicer. We're going to miss our little yellow shadow, who followed us from room to room, making sure her humans never got too far away.
Here's the last photograph I took of her.