I have to ask - was this suit for your age child? Also, is this device designed to be automatically make the child go face up? I doubt it. It sounds like something that should be used with adult supervision, so you should always be near your child in case anything like this occurs.

I'm so thankful this incident ended positively and no harm came to your child.

ps I would always treat something new like this carefully until your child is comfortable on her own in the water. In other words, if she goes in the water, go in with her and see how it acts before leaving her to her own actions.