SWA has always dipped back into the pool of highly qualified candidates who for some reason weren't selected on the first try. I recall the time I got a call from a friend who had been turned down for the 2nd time (great guy BTW) & told the story to the CA I was flying with...he then relayed his story to me of how he was hired on his 4th try....he didn't even think about it after all these years & was glad he was persistent.
Hang in there & update your app at the first available (1 year from the interview) date...if you were good enough to get the call the first time it would bode well for you that you could get a subsequent call. Thanks for your continued interest in Southwest....good luck!!!