We're awaiting OP's return so we know the complete facts. At least, I am.
Was this a Ponzi scheme covered by those special rules?
Is the entire loss a theft loss, or might there have been a market decline before the theft?
When if at all would he get the capital loss if, say, pre-theft discovery, the value fell from 100 to 75 and then via theft from 75 to 10, the sale price.
Thefts that are deductible are deductible only in the year discovered, which is not necessarily in the year that he was "wiped out".
Where does this "rule" in Pub 547 come from, and would it support OP's idea of a capital loss?
Decline in market value of stock. You can’t deduct as a theft loss the decline in market value of stock acquired on the open market for investment if the decline is caused by disclo- sure of accounting fraud or other illegal miscon- duct by the officers or directors of the corpora- tion that issued the stock. However, you may be able to deduct it as a capital loss on Schedule D (Form 1040) if the stock is sold or exchanged or becomes completely worthless.
. We'd need to know who committed the fraud.
The misc itemized deductions that are not allowed from 2018 thru 2025 include
(3) the deduction under section 165(a) for casualty or theft losses described in paragraph (2) or (3) of section 165(c) or for losses described in section 165(d),
, so is this correct:
It sounds to me like you are dealing with sect 165(c)(2) loss which is still allowed as an itemized deduction.