Sudden onset memory loss, behavioural abnormality which recovered spontaneously after some hours may be a attack of brain stroke (Transient ischemic attack) or it may be rarely an episode of seizure (fits). Most of times Ct scan of head in these conditions comes normal. Do he Have any other risk factor for stroke like high BP, diabetes,  Heart disease , smoking? Get a proper evaluation for stroke and seizure because if it is not diagnosed , he may develop further problem