How LONG after departure? Reason? Where was the flight's scheduled destination? You could listen to the departure feed (LAX uses two freqs for departures - then generally handed off to LA Center). Need to know details-incl flight number of course! If it was turned back more than about 10 minutes after departure, then prob all happened w/LA Center - in which case prob can't hear it since the ZLA coverage is somewhat spotty out there...but always worth a try. Follow the flight from twr to take-off/departure and listen to the hand-off frequencies...search on LiveATC and see if the hand-off freq is carried with a feed. If they were diverted back to LAX, then check flight aware for a landing time and go back about 15 mins prior and you'd be able to hear SOCAL approach talk to them on the way back in.