According to the IRS: "The taking of money or property through fraud or misrepresentation is theft" the loss would have to be involved with a business to be deductible. file form 4684 for 2019. if it was not, there is no deduction anymore for a personal casualty losses including theft. if it was a business loss, you would also need to see if it's cover by any business insurance you have. then you would have to file a claim and the loss would only be the unreimbursed portion. if you don't file the IRS could disallow any otherwise deductible loss.