You will need to contact UPS to file a claim; Amazon will not be any help with this. Not sure if UPS will refund for the loss/damage of the item or just the shipping.

Here is a post with some helpful info and instructions → How to file UPS claim after using Buy Shipping.

You can also view Amazon's help page → File a claim with UPS.

Under Amazon's help page, it states that UPS will refund you directly; however, this is not always the case.

Amazon is officially the UPS Account holder, so they may issue the refund to Amazon. If this happens, check your Account Payments - Transaction View to confirm that Amazon has credited your account. If not, you will need to open a case with Seller Support and provide them with the UPS refund confirmation, the $ amount, and the Order ID# and ask them to return the funds.

Seeing that you sell perishable flowers and this may happen again, I would recommend looking into linking your own UPS Account with Amazon. You will still receive the benefit of Amazon Buy-Shipping protection, but if problems arise due to damage or shipping cost issues, you will be able to file a claim with UPS directly under your own Account and get reimbursed without having to go through this.

Here is the link and help page if you're interested → Manage your carrier accounts.

Please keep us posted, and good luck!