I feel really bad for not saying thank you when a man held a gate open for me?

I was on a walk at my local park today. I was approaching a gate that a man and woman were walking through. He held it up for me. Just as I was walking through the floor became slippery and I almost fell over. I was pretty embarrassed, couldn’t make eye contact and just sort of rushed through wanting to get away. I feel terrible for not saying thank you. I wish I knew him so I could apologise:( is it that bad?
I feel really bad for not saying thank you when a man held a gate open for me?
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