I found this story -- believe it or not -- on TV on The Florida Channel had a great Florida Crossroads show on old forts and the early underground railroad (link to the video) - which went south to "free Florida" before it went north.
Florida's Historic Places:Fort Mose and Fort Gadsden
Perhaps Florida’s first mention in the history books came when Spanish Explorer Juan Ponce de Leon set foot on the shores of “la florida”. Since then, Florida’s role in American History has been an important one, and its land has often been a place of refuge for many. In the first part of an ongoing series, Florida Crossroads visits the sites of two historic forts - Fort Mose and Fort Gadsden - that you won’t find on a road map today.
The show is very interesting -- I checked out the Fort Mose website where I saw the phase "Black Seminoles" -- I then found myself reading about
John Horse for a couple of hours (I got in trouble for goofing off...)
It even had a tie to Sarasota

"Encampment of the 1st Infantry at Sarasota, Florida." 1841 watercolor by Seth Eastman. While stationed in Florida, Eastman may well have met John Horse, who served as lead guide and interpreter for the commanding general William Worth. Peabody Museum, Harvard University.
This is really a good story -- I have read about the Seminole wars some and never - never got this side of the story.