Davis403

When i bought the car i was told that it hadfno alarm system however when i got it home i noticed the interior motion sensors sensors . Further investigating revealed the blinking light inside the glove box next to a key slot .I am told that there should be a key to disable the system if necessary but no key came with the car and the dealer was unable to help. If this system goes wrong how to deal with it and still be able to start the car .