The PCB is apparently a multi-layer board without exposed traces for the button, so I couldn't cut traces. I didn't know how much heat the parts can take, so I didn't hot-air desolder the switch. Instead, I found a stripped-off piece of vinyl jacket from some audio cable that was just big enough to surround the switch plunger. I cut a ring of the cable jacket just thick enough to hold the exterior red button cap away from the switch plunger. Now pushing down on the red button cap mashes down on the vinyl ring, but the vinyl ring is incompressible enough to keep the plunger from being depressed. Now I just need to figure out some alternative way of dealing with carjackers that doesn't require use of a panic button.