That was a good story - and yes - two of mine have disappeared down the backs of couches - the first was our BP when she was just a few months, then the hognose. It's often difficult to find them in those couches even when you KNOW they are there. I had to keep reaching down and dragging my hand along in that constricted place but we knew she was in that bit somewhere. It wasn't enough just poking my hand in and running it along a minute and if we hadn't seen her go in there I would have sworn after the first minute that she hadn't gone there. I really had to delve deeply and it was quite painful it's a really tight squeeze in there (just what they like!)
I hope yours turns up soon.