my parents forgot about my birthday & I feel hurt

I know this might sound a bit childish but it's exactly the way I feel and don't know to handle it.
The matter is that yesterday was my birthday and I did not receive a phone call by my parents. I think they just forgot about it. It's the 1st tome this happens in my whole life (I am now 27).
I know it's silly but it hurts and I feel also a bit of resentment and anger.
My mother lives 300 miles away. I don't see her often. She gave me a present for Christmas-and-birthday altogether on Dec 25th. I do not mind about the gift (money), but I would have appreciated much more a simple call from her or a short message on my Cell Phone .
She called me tonight and did not mention at all the birthday. She asked me the usual things she asks me about my daughter and since I was a bit silent and uneasy she asked me whether I was tired.

I feel bad. I feel sad. Need some insight to work it out.

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