How can a friend forget that my mother passed away?

As you know it’s Mother’s Day and it’s the second one with her deceased. It’s super difficult because our mom is no longer with us but I did things in memory of my mother.
One of my friends texted me and asked what did I do for my mom on Mother’s Day. I told him last year that she passed away. He probably forgot. Don’t real friends remember?

I just don’t feel like responding to him or anybody. Sounds rude but that’s how I feel. I’ll answer him later or tomorrow.

How can a friend forget that my mother passed away?
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