We recently found a heptagon hidden on the underside of a Wegman’s rectangle cake, in a design all around the edges. (I’m no longer sure why we thought to look at the bottom of the cake, especially since I’m pretty sure we hadn’t cut into it at this point.)
The heptagons are subtle, because they’re not regular and they look like they’re masquerading as either hexagons or octagons. But they’re there:
In retrospect, it might not be too surprising. Wegmans is, after all, the store that thought to put heptagons and nonagons on the design of their cookie cakes (from back in the day when I thought heptagons were unusual, instead of all over the place).