Feel so sorry for you dear! Don’t brood too much over this incident and end up dampening your cake decorating spirit!
Probarbly was a structural issue, I agree with the others – your cake needed much more support. If really you need to refrigerate fondanted iced cakes, bring it out and keep in the cake box at least 1 hour plus before its picked up – effects of condensation on the fondant would have worn out by then.
Also try incorporating styrofoam balls in your modelling, that will help to reduce the weight of the figures – by wrap the paste around the styrofoam, you won’t need to use so much much paste to build up your figures.
Cheer up, definitely this won’t happen again because now you know better!