There's a problem has been known for a long time. Sometimes creations disappear from Spore.com due to blocking, corruption, etc. It's hurtful when great things disappear.
I've encountered it again. A few weeks ago, your very old adventure "Skull Dragons" has been disappeared. Did you do anything in Spore or did it happen unnoticed by you?
Fortunately, there is an opportunity to download and restore the adventure. It is still available via the link:
https://www.spore.com/static/thumb/500/649/040/500649040665.png