Originally posted by Kryten:

if you don't have the rested buff anymore and are wet(like always in the swamps^^), stamina will regenerate very slowly. But it should still regenerate, as long as you don't run all the time.
The hit killing all your stamina is normal though, that happens when you block a blow that is too strong. Upgrades for your shield (or a better one) help with that.

True, I was also wet and not rested, but I could only walk. I've been through the situation of having the stamina bar depleted and trying to run and you still see the grey bar of it regenerating and depleting again (and the animation from the character). Not this time though. I knew I was dead so I just pushed the stick and looked at the bar to confirm. Nothing.

Regarding the blow, I wasn't wearing a shield or blocking. I wish I could've recorded it to see the replay.

Thank you for taking the time to answer. Maybe I'll try to repeat the situation and record it to show what I mean better.