If you filed your federal return by mail and are certain that it was not received, then your only choice is file it again - by mail.
Use the same address as for the original paper return. Include a short letter explaining that the original was lost and this is a resubmission.
Send it via certified mail, with proof of delivery (return receipt requested). The IRS will not accept emailed returns.
Then, be prepared to wait. The IRS is behind in almost everything they have to do during tax season and paper-filed returns take the longest time for them to process.
