You need to call the company from whom you bought the lens, and complain about its condition. State that you're not happy that a piece of sensitive optics/electronics was left outside in the rain unattended, and that you require a replacement. Notify them that - save for its unacceptable delivery location - it was fine, but you're not satisfied. Leave them to take it up with the courier, since they are the account holder with the courier company, not you. UPS will not care what you think, as you are not their customer. However, they will care what the merchant thinks, because they are UPS's customer.
When you buy something remotely, you're outsourcing the shopping and carting to the merchant. It's up to them to get the goods to your house in satisfactory condition. They outsource the carriage to the courier. That's how these things work, and that's how you need to follow it through.
Whatever happens, I hope you get a lens with which you're satisfied.


