I think you first need to email the Indian Consulate and get approval for the renunciation. Mention that you lost your Indian passport and attach a copy of the passport, if you have one.
Once you get the Consulate’s approval, you can apply for the Renunciation Certificate. After getting the Renunciation Certificate, you can apply for the OCI.
You have to email to passport.toronto@mea.gov.in and get approval for your lost passport for obtaining the renunciation certificate.
The process of surrender/renunciation certificate is 4 to 6 weeks. After that you can apply for your oci.