The problem isn't that there doesn't exist a sentence that maps onto only the meaning that Ayn Rand is your mother, it's that there exists a sentence which one

The problem isn't that there doesn't exist a sentence that maps onto only the meaning that Ayn Rand is your mother, it's that there exists a sentence which one could reasonably arrive at that maps on to both the meaning where Ayn Rand is your mother and the meaning where she's not.