Assurant return concern

I am going through the same thing I put my device in the return envelope. Put it in the drop box at my apartment and it has never been scanned in and it's missing. I filed missing mail and search mail and it's still missing. Either the mail lady or guy stole it or either it's a scam going on. I contacted assurant to let them know and they said that they usually recommend for customers to take it to the usps instead of drop box, I simply told him I followed the directions that was given and it said I could put it in my mail drop box, a usps drop box, or take it to the usps myself. They said I am responsible if it's not found. How can I be responsive when I followed all directions that was given? We also have cameras at my apartment complex that would at least show me walking the envelope to the mail box. This is crazy that all these things are similar and they're not doing anything about it but over charging people for a phone that they already pay monthly fees for insurance on. It seems like a scam and the prices are ridiculous, they are fraudung people. And I'm sure and lady or female postal mailers that are thieves know that the company assurant deals with replacement and damaged phones so they will steal them if they have opportunity. Something need to be done about this!