Toyota — Toyota crysta navigation memory card missing

Address: 560010

I had left my innova crysta vehicle bearing reg. No. Ka04mr7942 for repair at ravindu toyota body shop on 18th feb 2017. After taking the delivery of the vehicle on 7th march 2017, i found the navigation memory card is missing from my vehicle. When enquired about it with toyota service supervisor, he says it had been returned at the time of taking the vehicle into their possession for repair which i dont agree with. I it was so, the same thing should have been mentioned in the walk - around check sheet which clearly has not been done.
We also found that there is no provision to mention of this very important part of the vehicle any where in the check sheet. Hence we did not realize about the memory card being left in the car before handing over the vehicle.
Please help us in solving this issue of the missing memory card.