I made some decorations for someone, and she put them on top of a cake iced with tub frosting. When she served the cake the next day, the decorations had all wilted. The bow was MMF with Tylose mixed in, and the rest of them were just MMF, but they had all been dried for a couple of days. She didn't put them in the fridge, and she didn't put the cake in a sealed container, just loosely draped it with plastic wrap.

I don't use tub frosting and am not planning to start but occasionally I do make decorations for other people. Is it common for fondant to wilt on top of tub fosting?