Is basic arithmetic something that can be forgotten? Studies have suggested that even infants have an understanding of basic arithmetic. There is a reasonable likelihood that it is something innate.
As we're only imagining anyway, let's ignore the genie for a moment. If we did lose our sense of basic arithmetic all of a sudden what would life at its core even be like? If there were two apples on a table you wouldn't be able to comprehend what happens if you took one. Would we even be able to function like that?
You're taking the analogy too literally. The point that I'm trying to make is that in math, and a lot of areas, is that concepts build upon one another. To understand something at a 7/10 of complexity it first needs you to understand the 6/10 concepts that it builds upon.