Thanks guys. I appreciate your words of encouragement. So far, no luck, and Z spent the day removing everything from the room one thing at a time, so that we could check every little corner, crevice, pocket or book binding. Still no luck :-(.
I know these things happen, sometimes, but WHY does it ALWAYS have to be a favorite snake who goes missing? Before, it was Rose Tyler. Never did find her. Now it's the little Tessera. Is Someone "upstairs" trying to punish me for some reason? I dunno. We'll just keep on looking, and hopefully we'll have good luck finding it alive and well before too long.