If you do not have a 1099 in the taxpayers name and SSN why would you even try entering it.

Just report the income directly on the schedule C as other income - put a description in if you want to. But there is no need to try to input a 1099 NOT IN THE TAXPAYER'S NAME ( or just about any other time either). Report the income on the correct form and move on.

You may wish to let your client know they are giving out the wrong information to the preparer of the 1099, and be prepared for an IRS notice to the actual recipient or backup withholding to possibly show up in the future if it is an ongoing payment stream.