I baked, filled and iced 2 cakes yesterday and put them in the freezer last night in preparation for applying the fondant today. I forgot them in the freezer and when I woke up this morning, the buttercream and the cakes were completely frozen - they were NOT covered. Do I leave them out on the counter to thaw? Will the buttercream be ok?? Should I start panicking?

I don't freeze my cakes but everything I've read here on CC tell you to let your cake thaw at room temp before applying your fondant and it should be ok. good luck

No don't panick! It should be fine. I would set it out a little before covering with fondant.
I just made a 3 tier cake and put it in the fridge overnight after frosting and covered it, it was fine. IMO it's easier to cover a cold cake.

I am sure someone else will come along with another suggestion.
I think it will be fine! Good luck!

thanks for your replies! So i should stick it back in the fridge before applying the fondant? Moreover, how do i "stick" the cakes together and on the cake board, with royal icing?

I would just take them out of the freezer and cover as you normally would covering it cold is ok.
What do you mean by stick them together? Are you stacking them? I am not sure what you mean. Need more info.
I usually glue my cakes to the cake board with buttercream.