Um, not to pick a nit but. They do store honey. The cell they use is called, by the folks that work with bumbles, a honey-pot. Early on, when the colony is small most of the sugar is consumed rapidly, little is stored, but as the colony grows, carbs can be stored as honey. Not much, but it is considered honey non-the-less.
I refer you to page 36 of Heinrich's bumblebee economics where he describes a hive having 195 ml of, you guessed it . . .honey. Now this is an unusual amount, but the simple fact is they store honey. later in the paragraph he says "incidentally, the honey tasted superb - we all agreed that it tasted superior to any honeybee honey we ever tasted."