Lisa Sarber Aldrich, from Michigan, visited her local Meijer store (an American hypermarket chain) to buy a cake, and asked the staff member behind the counter if she could ice a 'Happy Birthday' message onto it for her.
'She said she would, and after a long time, she came and presented me with this cake,' Lisa recalls in her Facebook post about the event.
'I looked her in the eye and said thank you before I even looked at the cake. After looking, I nervously laughed and headed to check out- it didn't really matter to me that it looked so bad - I thought people would think it was funny.'
However, whilst Lisa laughed off the somewhat unusual decoration without much thought, the other staff took the matter more seriously.
'The cashiers at the self check out didn't think it was so funny though, and called a few more cashiers and a manager over to look, even taking pictures,' she adds - but there was a twist to the reason for their interest.
'To my surprise, after they discussed it, one cashier put her arm on my shoulder and said "the girl who wrote that has Autism. Thank you for smiling and thanking her- even though she's not supposed to write on cakes, you probably made her day." So I guess the moral of the story is that kindness is important!'
Lisa's post received more than 140,000 shares from people touched by her heartwarming tale. She's also been sent hundreds of messages from families of people with autism, thanking her for her kindness.
'I am totally overwhelmed by God's goodness, and how he has used this cake story!' she wrote in a later update.
'I am sitting here weeping and reading through 100+ messages from people all over the country who have a loved one with Autism, thanking me. I just feel the need to say again- I didn't do anything special. Be nice. That is all. I can't believe how awesome God is that he is using this story to bless so many people! God is so, so good.'
And for the handful of naysayers claiming the story isn't true, or was just a publicity stunt? Lisa has this to say: