No, you lose them all.
It is all or nothing. Landed successfully = 100% of perks returned, anything else = 0% of perks returned.
Unless they recently changed it. I'll look in patch notes.
(I know it's already been said, but) Nope, and nothing new about it, it has to be a ditch though so make sure you understand those rules (look up how to successfully ditch in the MAs for clarification, ie: not deep in enemy territory, can't be a bailout, etc.)
I got a question related to this: if the map changes and you're in a perked ride (and you don't land in time) it counts as a ditch, yes?