I just remembered that the storybook adaptation of Christmas Eve on Sesame Street makes it a bit ambiguous as to whether Kermit can see Snuffy. I've only read/looked in the book a few times, but the various plots and subplots (like the Ernie and Bert subplot and the Cookie Monster subplot) are all featured back-to-back-to-back without any scenes in-between them. Anyway, in the book, the Snuffy scene comes after the scene where Big Bird reads the list of explanations he was given, and although Kermit is not illustrated into the Snuffy scene, the last image of Kermit before that scene shows Snuffy right in front of Kermit as Kermit looks down at his list. I assume that in the book's depiction he perhaps looks down before Snuffy appears, turns his head, and leaves without noticing, but I would assume that the adults would believe Kermit if he did see Snuffy. Keep in mind the book came out in 1981 or '82.
And I wonder if he really did get stuck. He asks if Big Bird knows how Santa gets out (and Big Bird thinks he found out how Santa gets down the chimney based on Snuffy getting his legs in the barrells, when Snuffy didn't get his whole body in). He probably did get stuck, but something tells me he wasn't stuck that badly (I wonder how Jerry Nelson or whoever was inside the costume at the time felt when his legs were in the barrell). And even if Big Bird did go out to get one of the adults for help Snuffy would have probably managed to get his legs out by the time an adult agreed to help. If I was Big Bird I'd probably just say that "a friend" got his legs stuck, as opposed to Mr. Snuffleupagus.
I recall reading an article from a few years ago about Buffy St. Marie, which said that Buffy was the only adult who did see Snuffy. That's the only time I've read about her seeing Snuffy, but if she saw Snuffy, she should have told the other adults. Surely they would believe her. And I think her people in Hawaii saw or believed in Snufflepaguses, which the adults didn't when they visited and heard a legent of Mt. Snuffleupagus.
There probably wasn't such an episode, but considering Olivia wasn't in the episode where the adults saw Snuffy, it would have been funny if they did an episode where the others tell Olivia they saw Snuffy and she didn't believe them. Considering her behaior on the subject in episode 1836 (and the voting episode) she seems like she'd be too stubborn in her disbelief to believe even the testimony of the other adults.
I've mentioned how when Big Bird talks about Snuffy to the other Muppets they don't have the same annoyed reactions, but it is interesting how in episode 2096 Big Bird seems to only care about the adults seeing him. None of the Muppets are involved (except Elmo). Frank may have been busy with the start of his directing career, Jerry (and maybe also Richard) might have been busy with Fraggle Rock, and Jim might have been busy with everything, but it's still a shame they didn't try to work around their busy schedules for such an important episode (Kermit could have reported on Snuffy's sighting).