So I long Rest, the Tinker beside me throws his Elixer on me. I pick up all my discardsm. Then long resting k8cks in and I heal 2, shuffle no discards and lose 1 of zero cards. This works, yah?
Correct. This case came up in the official FAQ. You would simply perform every step of the Long Rest except the loss of one of your discards.
The same would also be true if you long rested with 2 discards, lost both to ignore damage from an enemy attack, and therefore had zero discards when your Initiative 99 came up.