I don't recall them in the areas of LAX I usually transit (admittedly, often the UX gates), but you can just talk to someone at the gate to get them printed. Explain that you came in on a flight and need your return BPs if possible to avoid having to go through the hassle of going out to ticketing and back. They'll ask for an ID and that should be it.

That's what I've done 95% of the time and have had no problems--only a couple of times have they even wondered how I had gotten through security w/o my BPs.