If the loss occurred in 2017 and it’s a personal loss, it may be deductible as a theft loss. The loss is treated as an itemized deduction allowable only to the extent it exceeds 10% of adjusted gross income. Starting in 2018, there is no deduction allowed for personal theft losses. Of course, business losses continue to be deductible.
The difference between face value of a bond and lower market price, attributable to rising interest rates. On a sale, gain on the bond is generally taxed as ordinary income to the extent of the discount.