Yes, both plates have been stolen.
In that case you need to notify the police, and ask the police to complete a police report. Bring the police report to a DMV office to surrender the vehicle registration.
Wha should I do if my vehicle was stolen?
Your insurance company will: 1) give you 2 barcoded original NY State Insurance ID cards or provide you with access to your digital electronic NY State Insurance ID Card 2) send an electronic notice of insurance coverage to the DMV (your insurance agent or broker cannot file this notice) Your NY State Insurance ID cards and the electronic notice together verify your coverage. We need both. For more information about stolen and recovered vehicles you can visit our website.