Nothing is generated since your information is not entered into the system. If am correct you should be using the same Client ID as the one you got with PR.
Client ID (two groups of four digits) is a unique no generated on first contact with CIC, i.e. applying for PR and always will be your ref# in relation with CIC
Case number (UCI - a seven digit #) is only for Citizenship file/application.
If application is returned it is not considered started (UCI not generated)