The conspiracy just doesn't work!

[Formendacil]

I suppose it might depend when Sam made his last "report." We know that, on the day he was caught, Gandalf told Frodo about the Ring.

But we also know, from the same chapter:

Originally Posted by The Shadow of the Past

He was smoking now in silence, for Frodo was sitting still, deep in thought. Even in the light of morning he felt the dark shadow of the tidings Gandalf had brought. At last he broke the silence.

"Last night you began to tell me strange things about my ring, Gandalf," he said. "And then you stopped, because you said that such matters were best left until daylight. Don't you think you had better finish now? You say the ring is dangerous, far more dangerous than I guess. In what way?"

Given how the entire chapter from this point on is a complex dump of information new to the reader, I wonder exactly what Frodo DID know at this point, since we as new readers seem to be encountering everything for the first time now, but Gandalf and him clearly talked about something the night before. And, if they did, it is certainly POSSIBLE that Sam overheard it--though we would also have to posit that he reported this information that same night (or very early the following morning).

Again, this is possible--maybe not likely, but it's certainly possible that Pippin could have been at the Green Dragon the night before for that purpose, Tookland being quite close, or any of the conspirators, really.

Speaking of whom, I know that Folco Boffin is really just a name-shadow of Hobbits from the earlier drafts, but he's listed as one of Frodo's friends of as much closeness as Fatty--why isn't he in the conspiracy? Is he just one point shy of levelling up to that? In other words, why these specific four: Frodo's two closest friends, his gardener, and their most timid, creature-comfortly friend?

There are no (obvious) canonical answers, but fertile ground for speculation--or fanfiction?

[William Cloud Hicklin]

When we are rankly speculating, we can invent any excuse!

Maybe Folco was a blabbermouth and they couldn't trust him to keep the secret.