That’s awful op, where they with you an Xmas day?
This is thoughtless and hurtful, especially after you took them to get things for your ex. you should tell them how hurt you feel, they need know and ask them why they didn’t buy you anything when they always have before (albeit with ex’s help) .
When my ex left, I used to drive mine to the shops, (we live in a rural location) and give them money and tell them to go and buy me a present. Also did this for my birthday and Mother’s Day. Now they are older, the eldest two do everything by themselves, the younger ones ask me when I can take them to the shops and are always on the look out near Xmas. I have taught them how important thoughtful presents are, the need to buy paper and wrap. (My ex always asked me for my paper to wrap my presents!)
They all now really enjoy giving me presents, they buy me lovely presents, send gorgeous cards with kind words, little pictures etc but I have shown them amend also shown them how happy their input makes me. I wouldn’t leave things to chance or rely on your ex to organise.
I would take them to the shops now and say they need to get you something now, give them the opportunity to make amends.