When you select "Confirm" at the end of the 1099-INT section, the program returns to the Income Summary landing page in Desktop. Click Update next to Interest if you believe the Interest total doesn't include the item you just entered.
In TurboTax Online, the "Confirm" button appears with the list of entered interest and dividend items only, and when you click Confirm it takes you to the income summary.
With either version, you can return to where you entered the item if needed.
You might also have had an interruption in Internet connectivity at the time you entered the item. Refresh your online screen, or exit TurboTax and start it again to see if the item reappears.