I heard Sad Tristan Noises and went to see. He had discovered an exciting stash of candy in a boot above his crate (we keep our shoes there so he won't carry them around and get them dog-saliva-soggy). It seems he was exploring. As I watched, he stuck his nose in the boot, then sat and made more Sad Tristan Noises, several times running.
I think he wanted to play "swap me," only he was afraid of picking up the bag of candy because it was too tempting. Tristan is getting good at turning his back or leaving the room when he is too tempted by stuff he's not supposed to steal; I think the attempt at impulse control combined with the possibility of a treat for "swapping" a found item was creating too much of an internal conflict for such a good Tristan puppy to handle.
(The candy was removed to somewhere safer, and Tristan got praise and carrots.)