Well - he's the senior person in this - so he has to have most to lose. I would go in - head held high and pretend nothing has happened.
You are single - so you've not really done anything tho be ashamed of. IF he is married or in a relationship he's the arse and people will know that.
If all else fails - deny everything - only you and he actually KNOW what happened - so you could just say you shared a cab, or you went for a coffee - just because you left together does not mean that anythinbg happened ! IYSWIM !
As for him - I think it's up to him to approach you if he wants to discuss it, shut you up or even see you again !
Good Luck !