I noted recently that there is a tower site for the Palmetto P25 system on Edisto Island. That's the APCO 25 system that Charleston Co. and Beaufort Co. are using. So you might not find them on the traditional APCO 16 Palmetto 800 system. And there could be a yet-to-be identified Palmetto P25 site in Walterboro that is not listed in the database.
So if a wildcard for the Palmetto 800 system doesn't turn anything up, maybe search 851-860MHz for a P25 control channel. If you find one, analyze it (FUNCT+TUNE) and see if it reports SysID 1D9. If so, create a new P25 system with that control channel and use a wildcard to search for talk groups.