It's possible there were some time changes or flight number changes that caused DL to change routing. It would be helpful to know your original flight itin as booked. Also, the "Fare Details:" line in your email receipt will have the fare component details with fare basis codes. ExpertFlyer does not show any D1 fare filings for YYZ-PSP which is why there are no D1 options shown when you do a flight search for YYZ-PSP. I did a back-dated search on ExpertFlyer and it's not showing any historical D1 fare filings either. Did you originally book some other routing and they switched you to JFK-LAX routing?