If your project manager is still out of town, your best bet would be to stay with that position and continue to do your best to excel at it and get more time under your belt. If, on the other hand, your manager is back in town and you are now back in an HR role, it's time to think about how to make a move. I don't know a lot about your background, but the best way forward is often to take the skills you do have to the next level, which would be an HR team lead role. From the team lead role, you can work your way higher up the management food chain.
A project management career is best defined as a series of steps, a gradual transition where you move further and further away from the hands-on work and more and more into a strategic capacity. For each person, the steps are different, so you have to chart your own course. What I can tell you is that the most important promotions you will get will be from your current employer, or from a future employer that sees your potential and takes that crucial chance to give you bigger responsibilities. When you get that chance, it's time to shine, and then you are well on your way.
This was first published in March 2006