I could not find a matching issue, sorry if duplicate:
The Potion effect display bar has the text and icon when you are hovering over an item or hovering above the hotbar, and it disappears when you remove your mouse from the hotbar or item. see video:
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Well, maybe more than a minute. I'm in the overworld in Hardcore mode right now, and the bug isn't appearing. I first observed it in the Nether, with a Potion of Fire Resistance II (drunk, not splash). It may only happen there.
Pointing at an inventory item displayed the potion effect and remaining duration. Pointing anywhere else showed the empty box for the effect, but not the effect or countdown.
I looked at the issue this case is marked as a duplicate of (MC-35643). That issue includes this one, but I'm not sure it is this one. I experienced this specific bug without the symptoms of the other case in 1.7.2.
I suggest separating and reopening this issue. Will post screenshots shortly.