cellphone lost in less than 15 minutes

I hired a car with Tempest everything was perfect until when i returned the car i forgot my cellphone in the car cause i was busy on the phone while collecting my other belongings i went back to them after 5 mins and the guy that took the vehicle after me to go fuel it said there was no cellphone and i used the cellphone in the car phoning my lift putted it on the passenger sit took out papers out of dashboard n went out locked the car and hand over the key but when i came back after 15min my phone is switched off the person that took the car from the parking is not reachable and i waited for an almost an hour till he came back from filling the vehicle and the staff were defending him and i phoned to complain to the main branch in jo'burg i was sent back to kimberley branch. I know the clause that whatever was in the car if its lost is not the company's fault but i came back immediately and i left the phone there cause i got off the hired car into my car on my way home i realised i left my phone and i went back n it was switched off. Tempest must just look out for their staff cause really my phone was in that car n it was taken by their staff member