The Form 990-T would have been prepared by the IRA custodian and filed with the IRS. The Form 990-T reports income to the IRA (Unrelated-Business Taxable Income) that is taxable to the IRA despite the IRA normally being a tax-exempt trust. The IRA custodian properly used funds in the IRA to pay the tax. This payment of tax is effectively an investment loss within the IRA, so it is not reportable anywhere on your tax return.
Perhaps the Schedule K-1 was sent to the IRA custodian since your IRA, not you, was the member of the partnership and it's the IRA that has the Form 990-T filing requirement.
