If you're pause mode - the health bar does not change - but he drinks. You can see this after you unpaused.
And to comfort you - it happened countless times to me in the midst of a battle => I had overseen my char had the potion button highlighted - so my DK got nothing <img src="/ubbthreads/images/graemlins/shame.gif" alt="" />
no i know that, i heard the gulp for him and it doesnt move anywhere.
I know for a fact it's bugged because both guys had half hit points, i heard the gulp, unpaused and NEITHER bar went up nor down on health.