Mechanic might be stealing stuff from my parents car

I suspect the mechanic has been stealing items out of my parents car when it goes in for work or inspections, we always find stuff moved around, recently though it came back after work and several items are missing.

It went in to have an engine part replaced, when it came back i noticed it looked like someone had gone through the boot, things moved around from what i remember, and it's suspicious considering that this work was only in the engine bay, none of it involves going in the back, they have done whole inspections before without going in the back.

One of the things i noticed immediately was my geiger counter, which was left on the parcel shelf, was not there.

I have searched every nook and cranny, the entire boot, underneath the seats, and have not found it, in addition there was two ham radios which i also cannot find.

The missing equipment totals about £150

Due to the low value i didn't put trackers on them, so i can't locate them.

My parents say there's a small chance they thought the equipment was theirs, but i doubt it, the geiger counter literally says radiation detector on it twice, and the ham radios are clearly radios, a 30 second google will tell you this stuff is cheap junk, which is interesting, why would someone steal this?

What should i do? my parents say they'll contact the garage, i thought police but i'm not sure if going to the police is an option since the theft is below £200, should i leave an irresistible bait in it next time that's got a tracker?