What do you do when you have been punched by your boss?

I work as an assistant manager for a large national pub operating company. After a staff party at my pub; myself, the unit manager and a team leader were sitting and discussing work matters. The discussion got a little heated between myself and the team leader and the manager got involved and also quite angry and asked us both to leave. I tried to calm the manager down as did the team leader. During this time the manager actually punched me in the face and said that if i didn't like the way things were run there then i should quit. To this end i replied fine i quit, gathered my belongings and left the building. I informed my area manager of the circumstances. I did not show up to work the following day as i felt unable to work for the manager in question. I had a meeting with the area manager and she took down details of my recollection of the events and said she would investigate matters further. Following this investigation it turned out there was no cctv recording at that time and the team leader and the unit manager denied all knowledge of her hitting me, stating that myself and the team leader had an argument and the manager asked me to leave after which i did so. There was no evidence to support my version of the events. The area manager gave me three options: to continue my resignation, to consider transfer to another pub/brand or to return to the pub and resolve matters with those concerned. I explained that i did not feel comfortable returning to the pub after what had happened and felt that the area manager should not expect that of me and should find an alternative unit for me to be employed. The area manager then explained that they had done all that they could and that as that site was my original place of employment that i would have to return to that site until an alternative site could be found. I would like to continue employment with this company but feel i have received a 'bum deal' from it all and would like advice as to how to resolve this situation and continue with my career within the industry. Any friendly constructive view would be appreciated. Alex Doggett