if you recall and command your champion to the edge of the "buy circle", which is something that like everyone learns to do as a recognized best practice, when you buy tracker's knife (for the first time) it enters your inventory with zero charges.
Can confirm, happens to me all the time and it's annoying if you don't notice it and go out to realize you have no wards..
Wouldn't really say it's a bug. It's the same as homeguards. You need to go into the fountain to receive the boost. Though I'm not sure how it works with the new potions so it may be a bug. My money is that it's the same scenario as homeguards.
