Why is my refrigerator not cooling?

This morning when I came in the kitchen I noticed that my refrigerator door was open a SMALL bit. I noticed that the items in the fridge had formed condensation on the outside. Nothing was spoiled but it was just not normal. So I closed the door and came back hours later to get a bottle of water and the fridge didn't seem to be getting much cooler. I looked in the freezer and there did seem to be some ice crystals toward the back of the freezer but not underneath the pan at the bottom of the freezer. I looked in the fridge and there is no leaking or water anywhere, but there is condensation at the top of the refrigerator near where the lightbulb is and back behind that. I can hear the fan working in the freezer and it does sound like the fan is working in the fridge but I can't distinguish if it is just the loud freezer fan or the fridge fan that I'm hearing. I am not sure if this is caused by the fact that the door was left open or by something else. Does anyone have any suggestions? Of course we just went grocery shopping and would hate to have to take everything out and thaw the fridge if this was just caused by the door being left semi-open. Any advice would be appreciated. Oh, and we have a Roper by Whirlpool fridge with the fridge on bottom and the freezer on top. Thanks in advance for any help!!! :)