How do i check if I have my 2015 tax return already on file? I don't want to pay for no reason, if I haven't already started.

I believe I signed on and started to file for 2016 taxes, but then had to stop due to the AGI or PIN not being found on my end.  How can I be sure my info has already been entered?  I made an error with my original header, I am inquiring on 2016 taxes not filed,  not 2015.