Hi--the chances are very good that he will regain his memory except perhaps the immediate period about the attack. Sometimes that never comes back but it means that he would only have lost a day or two. The more distant the event, the better his memory will be. Just anticipate the rest coming back over days to weeks.
Why did he have the seizure, do you know? Had he a history of seizure prior or was this new?
And when did he have the seizure?
I do wish to discuss this with you and spend time on it as, if the seizure was associated with heart stoppage or other serious cause, he may have more trouble with regaining memory
The important thing is that his seizure not be repeated and a cause for it is found, if it hasn't already been.
A half-hour seizure is a serious and long episode.
(I'm waiting for a reply now. I was answering someone else who messaged me before.)