I delivered a fondant covered (buttercream filling and crumb coat) wedding cake yesterday morning that had been in a cool, dry finished basement overnight and an air conditioned car for a 90 minute drive to an indoor reception room. Is it possible that a bubble could have formed on this cake at the reception? I am hearing all of these horror stories (and it was very humid this weekend) and now I am wondering WHEN exactly does the bubble start to form. I am assuming since it sat out at room temperature all night I should be in the clear. Any thoughts?
It happens, unfortunately. here is a thread that might help.
It sounds like you are taking all of the right steps. Make sure you use a fondant smoother tool as you are applying the fondant. Also, bring a small pin to poke any air bubbles and your fondant smoothing tool and you should be good to go. As long as the cake doesn't go through any huge altitude or temp changes.