Changed battery- factory alarm sets
 

I had to replace the battery today, I knew that the alarm would arm itself....but I had forgotten that fact. I had to hunt down the remote for the alarm, found it and all's good.

However, "what if" the battery in the [one and only] remote was bad and I couldn't disarm the alarm system with it...how else could I disarm the system?

Open the door and start the truck with your chipped key

Just to clarify: You mean leave the door open while starting?

No. Well I don't think it would matter. It may disarm by unlocking the door with a chipped key also.