Who did you purchase your ticket through? If it wasn't directly purchased from DL, you may want to find out why the third party booking site or person didn't contact you. If you purchased it directly from delta.com or over the phone, make sure your skymiles information is correct or that your contact information is correct and you are opted in for receiving email from delta.

I have had multiple emails for changes in my itinerary for as little as 5 minutes all the way up to a major schedule change (DTW-HKG suspension). Out of the majors, DL is annoyingly persistent to make sure you are aware of each individual schedule change.

I don't know what the exact time frame is for refunds, but I think 120 mins outside your original schedule time should fall well within that time frame of being eligible for a refund. What did DL say when you asked them about a refund?