But then the brother probably also answered with "I don't know," so the mom had to ask someone else. And then the next person probably said "I don't know" too. Did the mom ever get the true answer? IDK.
Hopefully this exchange wasn't the end, but just the beginning. And then they spent the next several years texting each other, thinking they were mother and daughter. And then they lived happily ever after.
On the one hand, this is a pretty huge mistake. On the other hand, if you're willing to spend $60 on fish without batting an eye, you're probably doing all right in life. No need to feel too bad for this person.