Well, Fatty is more of a footnote too. I guess Folco was even more Fatty than Fatty, if you get my meaning.
I guess that for whatever reason he was excluded from the conspiracy, and, not having such close ties to the 4 main hobbits as, say, Farmer Cotton, he does not make any further appearance onstage.
As to what happened to him - my answer would be: that's what fanfic is for.
