My 17 year old son in the past year has short term memory lost. He will look disoriented and them ask questions; such as, where is the bathroom or his bedroom? He usually realizes he just asked a strange question and just blows it of and does not seem concerned. Ask first we thought he was joking, but he continues to have these episodes. I had a brain tumor in 2010 so it makes me nervous even though I know my tumor was not a genetic medical problem.
Hi, He merits a neurological examination and very likely some form of diagnostic testing such as an electroencephalogram, MRI of the brain, and possibly blood tests.  He or someone should keep track of his forgetful spells on a diary or calendar which should also be taken to the doctor for review and analysis.  I would recommend a neurologist examine your son. Hope I have answered your query. Let me know if I can assist you further. 