If you used the TurboTax Business CD/Download software installed on your computer to prepare and file that 2016 return, you would have had to save a copy of the PDF and/or tax data file to your computer. TurboTax does not save copies online when you used the CD/Download version of the software. Only returns prepared and filed in TurboTax Online are stored in your online account.
NOTE: If you are referring to a 2016 return you prepared and filed online, you need to log into exact same account you prepared it in last year.