If the person just had symptoms chances are that it is a new infection that just came about in the past 30 days, probably in the last week or so.
If your friend tested negative then he does not have gonorrhea. Unless he has aquired it orally at some point and passed it on that way. The only way to find that out is a throat swab.
I would advise testing for chlymida now, syphilis at 6 weeks and HIV at 3 months.