Oral is not low risk, it is zero risk so you don't need to test for that encounter, or even think about that.
A dup is conclusive after 4 weeks but any other takes 12 weeks. If he took a duo he is conclusively negative, but if it was anything else his status is unknown. Do you know what kind of test he used or where he took it so you can call them to see what kind they use?
Don't bother with the RNA since the duo will do the job.