Hi
isfleming, welcome to the site.
That is most likely a bogus ID.
Questions to consider are:
Is this ID recurring repeatedly ?
Are you hearing anything on it ? If so... is the same conversation continuing on a
known talkgroup ?
Looking at the database, the last known tg's are in the high 26800's ,
and I can't imagine that there would be a valid one used so numerically
far away from them. :?