I just found out that my tax preparer did not actually file my taxes. Is it too late to file for an extension?

It is too late to file for an extension ... just file the return asap. 

Did you use Turbo Tax?  You can efile until Oct 15.  After that you have to print and mail.  Is your tax preparer going to finish filing your return?  Did they give you a copy?

Another question is your tax preparer going to bill you for the shoddy work and in effect be in violation of the TT agreement (not for use by those who charge for return preparation). If the preparer is charging you then under IRS rules they're required to sign the return.