Bad service at shoprite

Good day I was in shoprite Newlands in johannesburg today and my gift voucher card fell out of my pocket, I got it from my pastor at the mosque early today however that was my only option to get food cause we don't have. Appearently someone I know was in shoprite and saw that 2 staff members were the once who picked it up and no one at shoprite including the store manager wanted to help us, we asked them to check their cameras and they told us they don't have any, she didn't even go as far as asking her staff members. I just wanna know what I have to do in order for them not to get away with it because it's not right.