This is (believe it or not) the way it is supposed to be. The basic potion of healing is not listed as a magic item, and therefore not in the potion section.
This is probably because buying magic items is optional, but buying gear is standard. So WotC wanted them to always be purchasable.
Potion of Healing is tagged as a potion and other gear, however if you filter for potions it is unlisted.
This is (believe it or not) the way it is supposed to be. The basic potion of healing is not listed as a magic item, and therefore not in the potion section.
This is probably because buying magic items is optional, but buying gear is standard. So WotC wanted them to always be purchasable.
That's interesting, I'd figure it would at least be listed under either filter. Is it actually not listed as magical?