Malware triggered by its absence? If the device disappears, it's likely because it was found and removed, so malware that starts erasing data or otherwise causing confusion or covering their tracks is a plausible next step (though not a good one in this case, given that the device itself led straight to the person who planted it).

- Being suspected or charged of destruction of evidence. It happened.

- Losing access to forensic data by not capturing the contents of the device RAM. Pretty common.

- Becoming witness of a crime and getting personally targeted by some criminal organization in retaliation. This one should be obvious.

- Wasting the opportunity to keep the device on to monitor the activity of the intruder