I don't quite understand what the problem is. Delta isn't interested in selling tickets from FLL to ISP on December 4th, and you don't have the problem of holding a ticket for a nonexistent flight or anything like that. You haven't bought a ticket, right? The solution seems pretty simple -- fly Southwest or some other airline. It's not "fishy", it's just Delta changing fares and schedules a thousand times a day like any other airline.