It's implausible that TurboTax would transmit an e-filed a tax return without it being electronically signed. It might be that you e-filed your tax return without providing the identity-protection PIN. That filing would have have been electronically signed using your e-signature PIN (possibly carried in from the previous year's TurboTax tax file used to begin the tax return in question) but the failure to provide the separate identity protection PIN would likely cause your tax return to be rejected.
