Promotion promised but then taken away

About 3 months ago i was promoted to bar superviser. I had been working closely with the bar superviser for several months beforehand when he decided it was time to move back to his home country. My Operations manager pulled me aside and said to me "Brendon, with *George* (name changed) about to be gone I am going to promote you to Bar Supervisor. You will have at least 2 staff under you. He trained me for the position for the next couple of weeks showing me various stuff i didn't know. He got the previous Bar Supervisor to show me everything else mundane. The Operations Manager basically trained me in the more complex problems such as billing, using the computer for day to day bar tasks and how things should generally be done.
After 3 weeks or so the Operations Manager resigned and a new one took over. I am now stuck in the same position as i was before. The new Operations Manager and I get along fine and he generally is enthusiastic of me taking over the general tasks of running the bar but without the title. This in itself makes it difficult for me to control the bar and how things are run yet i am considered with medium responsibilty of the bar and it's contents eg If things don't add up they come back to me, the bar is left in a unorderly fashion, and if stocks have variances. I had a "Personal review" along with other colleages though seperately and he told me I was performing above average. He also told me that though the General Manger does not want a Bar Supervisor as yet I would be strongly considered for the job in future.
What am I to do, I feel as though i have a personal responsibilty to the bar and try to keep things in order as much as I can however I am of the same level as the other staff so I can't be demanding and if things do not go as I have planned I have no authority or control of how they are run.
Another thing. I have been trained of lately for other aspects from which my field does and does not cover.
I am currently studying at Uni in a different field of study and this is not my career choice but I feel that I am in a dilemma in the current situation.


Comments/Questions greatly appreciated.