When a player clicks the "cancel adventure" button (note, that this can happen by accident easily, it's just below the "send army back" button), the following window comes up:
cancel.jpg
http://bayimg.com/baNclaaeF
Now a player who do not want to cancel the adv has to decide: that cancel button will cancel the window (going back to the adv) or will it cancel the adv. itself?
I deciced it was best to just reload the game...