Ok folks.. long story short, I was developing on a computer that I no longer have access to. I was able to retrieve the source code, but not the .keystore file used to sign
If you have enabled Google Play App signing for your application you do not need to worry.
To check if you have Google Play App signing enabled, go to Release management -> App Signing, in your Google Play Console.
If it is enabled you can contact Google Play Support by filling the support form or else you can also opt for live chat with a support personnel here: https://support.google.com/googleplay/android-developer/answer/7218994?hl=en
Explain them your issue and they will tell you the next steps which include creating a new 2048 bit RSA keystore with 25 years validity and exporting the key to PEM format and emailing it to them.
To export key to PEM format:
keytool -export -rfc -alias upload -file upload_certificate.pem -keystore keystore.jks