Under the tax reform law that was passed in 2017 there is no tax deduction for theft losses for 2018 through 2025, except for Ponzi schemes. Some states might allow a deduction on the state tax return. This doesn't sound like a Ponzi scheme.
Are you sure it was a theft? If it was a bankruptcy or liquidation it might be an investment loss, which would be deductible, though not necessarily all in one year. Also, there would have to be no possibility of even partial recovery. See if you can find out anything about the status of the company.
