I would take the car back to the person who installed the remote start. Tell them what's going on, and that the alternator and battery tested fine. (In L.A. Autozone is the place to go) No matter how long ago you had it installed, they should have enough integrity to take a look. Sounds like a connection isn't intact.

If they fix it, bring them a 12-pack of whatever they drink. They're remember you if something else goes down.