The more you say you dont know why anyone would take it, the more reason to believe its right in front of you somewhere. Was there anything else of seeming value in car at time of alledged theft? If so and its not missing odds are you misplaced it.
When I thought someone stole my tuner from my spare tire area, I ended up finding it on bookcase in garage behind water bottles after I had gone shopping.
Point being, its right in front of you somewhere. You may have even dropped it in trash moving stuff around. Or under hood of car inside airraid box. In seat pocket. Under seat etc. Ive done all these before lol.