As Champ Mike9241 said above, with the dates being that close, that notice may have already been in the works when you paid or soon after, before it was fully processed.
If you are able to establish the IRS account as Champ Mike9241 described above, then your main IRS account also has a section that shows any payments that have been credited to your account.
https://www.irs.gov/payments/view-your-tax-account
