You say 'Panic Alarm'. Do you mean Burglary Alarm?
As a former Cop, people confuse and mix up the terms Burglary, Robbery or Panic Alarm all the time. But, they are very different things (to those in the business).
I'm not trying to school you on all that crap, but it makes me wonder; Where was your key fob? Any chance you, your pet or other family member rolled over on it, pushed the "panic" button or something like that from inside the house and set it off?
Just 'cause I brought it up, Burglary is breaking into something... house, car, etc. Robbery is taking from a person with force. Burglary Alarms are generally set off by the security system, or bad code. Robbery Alarms are manually pressed or triggered with a code or button. Panic Alarms are definitely designed to be manually activated, though malfunctions in all those cases do happen.
So, long story short, a Burglary Alarm would have triggered with someone Phocking with the truck. The Panic Alarm would trigger with your key fob.
Maybe the cat stepped on it?