Unless they made a payment with the extension that needs to be entered on the Tax Payments worksheet, theres nothing else you need to do... at this late of a date, the IRS either has the extension or it doesn't, there's nothing that shows up o the tax return anywhere about the extension unless there was a payment to include.

If YOU Efiled the 4868, the Form 9325 would indicate it, but if they filed it themselves or someone else filed it, the 9325 wont show it.