[Let's Go] Hidden Potion in Viridian Forrest

Hey! I have the guide for Let's Go Eevee and Let's Go Pikachu, and my guide says that there is a hidden potion in Viridian Forrest. I've checked many different walkthroughs online, and I've walked through the forrest myself in the game, but I haven't been able to find it. Does anyone know where it is? Thanks in advance!

It's behind a tree in the northeast corner. The item ball, if it's there, is actually completely blocked from view by aforementioned tree.