random guess--it looks like the waxed board did it's job of not letting the cake juices seep into it except around the outside edge--what do you do inside your cake pans? how do you grease them or do you use parchment or waxed paper?
i'm thinking maybe you hit a bump or two and the cake just became airborn and popped off because it was not attached--that's my best guess--and there could have been one of those air bubbles down there too--hovering under the cake--even though it was attached in the middle--just not enough to hold it right--
your method of greasing the pans could have exacerbated that by keeping the protective barrier on the bottom of the cake--you placed it bottom side down?
what flavor cake was it?
it really broke my ♥ when you said
ouch ouch ouch-- i feel yah
Oh, and the waxed board is completely filled with grease on the underside. Like it sucked out the moisture of the cake. We use crisco in our pans and dust with flour. The cake was chocolate and was placed bottom side down. It seemed almost dry on the bottom after inspecting it sideways in the van, but the inside of the cake was wonderful and moist as normal. I know that those silver drums don't suck the oil from the cake because they are sealed and that cake had been on that board since Wednesday. It actually fell about 2 minutes into the drive. I gently turned off my road onto the main road and it just plopped itself over.
Not sure what happened...but may I ask why you put your bottom cake on a board...then also on the drum? To me, this is an unnecessary use of that bottom board. I would think that..and the fact that the center dowel did not go through all the way to the drum...and a bad bump? I don't know...was your cake cold? I don't think you mentioned that, but I only travel with a cake that has been in the frig overnight. A room temperature cake is a dangerous cake ..my opinion.
sarge, i was conjecturing about a bump--op says she made a gentle turn that she's obviously made with every cake she delivered from there--just wanted to point out that i said bump--not op -- op says gentle turn
and i agree that a room temperature cake is a cake waiting to implode during delivery