Sounds like you really need to get some frames out and see if you have a queen or not. Start at one end and pry that frame over to the side. Then the next and the next until you get to the far side. Maybe even try to get some of the propolis off of the sides of the end bars as you go. When you get to the far side you should have a frame you can get out. Even if it's crowded, just go slowly and try not to roll the bees too much. Set that one aside and you now have room to get frames out. If you think they are burred down to the box below, then pry the box up first and then pry each frame over.
IF you don't find eggs or brood you still might have a virgin queen that isn't laying yet. If you have some brood you can add you can elemenate this possibility by adding a frame of eggs and young brood and see if they start a queen cell.
To be more accurate here's what you may find:
1) No eggs or open brood (and maybe no capped brood). Possible causes: They have raised a new queen who isn't laying yet; They are queenless.
2) Eggs with occasional doubles. Possible causes: They have raised a new queen who has just started to lay but hasn't got the hang of it; They have laying workers.
3) Lots of multiple eggs. Possibly a lot of drone cap and open brood. Cause: Laying workers.
Of all of these possible states only one will accept a new queen. The others are all a waste of a good queen.
If you decide you want a queen I have queens. www.bushfarms.com