The Ohio Dept. of taxation has sent me a letter saying they did not receive my 2016 return. It was filed with turbo tax. Where can I find it?

Did you efile?  Was it accepted?  If you efiled federal it does not automatically efile state.  You had to continue on through state and efile it too.  You can check your efile status here     <a rel="nofollow" target="_blank" href="https://turbotax.intuit.com/tax-tools/efile-status-lookup/">https://turbotax.intuit.com/tax-tools/efile-status-lookup/</a>

To access your prior year tax returns sign onto the TurboTax website with the userID you used to create the account - https://myturbotax.intuit.com/

Scroll down to the bottom of the screen and on the section Your tax returns & documents click on Show.  Click on the Year and Click on Download/print return (PDF)