Yes, you do as IRS will match up the 1099B with the return and if send a notice they use the gross sales price on the 1099B with $0 basis and make it Short term gain.
So that loss could actually be income if the IRS goes it.
The other reason is that loss can reduce the income on the return and you might be entitled to a refund.
TurboTax can walk you through the Amended return process.