THe dealer alarms are connected like other aftermarket units. Try to find the alarm module (look for a 3x3" black box) and look for an in-line fuse connected to the wiring harness. The parking lights might have one and the constant or switched power as well. They are installed 99% of the time under the drivers dash or in the kick panel.
HOwever, it's probably not a fuse if the alarm still works. Hack installers use T-taps and one of the wires probably just got loose. If the alarm even makes any kind of chirp then it's not one of the fuses. Just find the box and trace all the wires to check for loose connections if your not comfortable using a DMM.
