Chicken Stock - Absorbed all water?
You don't mention covering your pot, so I'm assuming you left it uncovered for the duration. If that's the case, you boiled all your liquid off. Next time you can try using a lid, that should slow the evaporation of water from your pot and leave you with some stock still in the pot. Even if the pot was covered, though, "a couple of hours" is a pretty long time for something that only had enough water to cover-- no lid seals perfectly.  Some evaporation is always to be expected, so you probably needed a little more water to start, or to have topped off the pot at some point.  

You may be able to reuse your chicken pieces and vegetables, but I wouldn't. You mention using chicken breasts. If your aim is to produce a flavorful stock, this is the wrong part of the chicken to use. 

Meat is typically used in broths, which can be flavorful, but chicken breasts are notoriously bland even when cooked whole. Stocks are typically made with bones and very little meat. Rendering the flavor and gelatin from the bones gives a rich stock using much cheaper cuts (or even scraps, if you have a recently roasted bird).  Price may or may not be a factor for you, but the result is usually far superior when using an appropriate ratio of bones:water. 

In your case your chicken breast is like so dry and overcooked at this point that there's not really any flavor left to impart to a stock/broth. You may have slightly better luck with the plant matter, but I doubt it.