Did you start a return last year in Online TurboTax? If so you can look in "Your Tax Returns & Documents" and see if there is evidence of a filed return with a "return status.".
If there's nothing there, but you think you did use TurboTax last year, we can tell you how to look for multiple accounts.
The IRS would probably tell you if you filed a 2017 return or not, if you wanted to phone them.
