When you throw a potion at the ground at your feet, it doesn't always activate. The icon does not appear in the upper right or in the inventory.

This occurred in my survival world, although I have been unable to re-create it in creative.

Given that this was a potion of strength, it may be connected with having slow falling or being near the dragon.

I also experienced this issue, which may connect: https://bugs.mojang.com/browse/MC-155798

Sorry for the messy post, I haven't really been able to determine what's going on, was hoping someone else would be able to find something that's more useful.