The way I would adjudicate is that your sage is only considered trapped if you have no stones left to play that can help you. If you haven't drawn all your stones yet, continue playing and see if they help. My 2 cents.
You are supposed to draw all of the stones you intend to play that turn at the beginning of your turn (emphasis is mine, but per the rules).
My question is about the legality of moving your Sage into a position such that your and an opponent's Sage are trapped at the same time (e.g., jumping over a whirlwind into a mountain enclosure containing an opponent's Sage with only one free space). Does one Sage's movability get resolved before the other?