Missing Media/Memory Card after service

I recently took my car in for service and forgot to remove a memory card from the car's system as this is just a tiny item and can be easily forgotten. I realised this when it was time for me to go collect the car that i forgot ths item in the car.When I got back the car from the delearship, the sound system was reset and tried to check if the memory card was still there but to my surprise it was no longer there.

I've been trying to advise the delearship of this but they say this was never in the car which is not the case.

Kindly assist with this matter as they are not taking me seriously.