Helping Buttercream Crust

Hi,

Recently I made a chocolate cake that turned out very moist. It was quite delicious at least the scraps were after trimming it. I think I messed up by frosting the cake while it was still partially frozen like I typically do with my other cakes. But this time the frosting did not crust up as well and this morning a chunk had come off! AAAHHH! I don’t want to have to completely redo the cake. I currently have a fan blowing on it while it’s in a cake box so it circulates around the cake. But I’m not sure that is going to work. The good thing is it’s on the back of the cake, but I’m worried that more will fall off in transit to the house in delivery!Any ideas on how to fix this without having to completely redo it? Help!

Thanks