For others who may be reading the thread, I think it's a great lesson in taking control of all avenues of redundancy you can. In this case, don't just have DL notify you via text; have them notify you via email also. And, especially during holiday periods, proactively check the DL app on your phone AND the DL website every few hours to ensure that your flight is departing when you think it's supposed to.

It's very possible it was your phone carrier and/or OS that glitched your cxl text and queued it up to pop after an erroneous "on time" text. Very hard to know if that was on Delta.