It's not clear whether you sold an investment at a loss, or if the money was simply stolen.
If there was an actual sale, and there are documents showing the purchase and the sale of the asset, then you could report it as an investment sale, which would produce a capital loss.
If the money was stolen, there is no deduction for theft loss for years 2018 through 2025, under the tax reform law that was passed in 2017.