What Happens When a Customer Doesn’t Sign a Contract

Question: I rented a large loader worth roughly $250,000 to a repeat customer,
a contractor, based on an email he sent requesting that I deliver it to his job site. According to my driver, the only person at the site when he arrived was “a big guy named Nick who was wearing one of the customer’s company shirts and a hardhat. Nick said he was one of the customer’s employees.”

My driver says he didn’t get Nick’s signature on the rental contract because he didn’t know if Nick was authorized to sign it. It is possible that my driver simply forgot or that Nick didn’t want to sign it. He also did not get a driver’s license number. The equipment disappeared, along with Nick, and the customer now claims I can’t recover for the loss because I don’t have a signed rental contract. I’d like to know if I have any chance of getting paid for the loss
or if I’m simply out of luck. What can I do to avoid this in the future?