Ok, quick lore theory and I'm out
(contains spoilers for Wings of Fire books 1-10 and Wings of Fire Legends: Dragonslayer. Only read this if you have read these books)
So we know how Palm was escaping from Torch, Arid, some other nameless guard, blah blah blah, and then Palm pretended to be Prickle, he sister, so she could save Onyx.
But what if Palm got captured instead?
Well first off, Queen Oasis would have a b s o l u t l y no idea about Onyx bc when Palm was escaping after Prickle got captured she saw three scavengers on horseback.
Coincidently, Heath, Stone and Rose were riding ON HORSEBACK to go steal treasure and kill Queen Oasis.
So, if Palm got captured instead, Oasis would've died anyway so she( Oasis) would have no idea Onyx was her granddaughter.
Now reading this, I realise that I read WoF over and over again