It technically didn't. I bought her back in April, with the chance of her being pregnant. But what I didn't know was the woman thought she was around 5 months at the time I bought her. When my vet checked in April she was "open" but her cervix was tight. Then yesterday she was checked again, cervi was still tight and her uterus had dropped below the pelvic rim, so my vet put her at 4-5 months along OR false pregnancy. Though the fact she was with a stallion puts the vet leaning toward pregnancy.
I get the fact, that normally you can't see an embroy until 16 days of conception, but my vet said with how malnourished she was to go as far as 30 days that you can not see the foal. So at the time we checked in April she could have been anywhere from 6-30 days pregnant, we had her checked not even a week after she arrived.
So yes, I knew about it, I bought her for a "two in one" deal. Which almost turned out to be a "one in one" deal, but now is holding true.