I was at work in a supermarket and I was manning the self serve tills. I see a man struggling with scanning with a newspaper as all the inside leaflets etc were falling out everywhere. So I go over to help him and ask him 'do you want a hand'.
I then look at him and see that he only has one arm. My face just drops into a look of horror as I realise what I just said and we just look at each other.
Luckily he just laughed as I was trying not to die of embarrassment and accepted my help. Honestly, I don't think I have ever wanted the floor to swallow me more than at this moment.
As he was leaving he waved goodbye with the flap of his coat where his missing arm was and I just went bright red whilst my colleagues laughed at me. They continued to laugh and reminded me of this for the entire day and I am not sure I will ever live it down.