My Saturday lift ticket was in my pocket.
My Sunday lift ticket was in my wallet — I just kind of forgot about it.
On Sunday it turned out the Sunday ticket was already used. RFID!
This is a little insane: say you have 12 discounted ($69 each) lift tickets in your ski backpack for some reason — you got them at REI for a bunch of friends who are arriving tomorrow. You forget to leave the tickets at the cabin. On your first run they've all been used up!
You just spent $897 to ski Squaw for one day and left a bunch of people without lift tickets.
The mechanics behind creating such a devastating disaster should be a little more complex than just getting on a lift.
At the very least those tickets should have some large warning in red letters.
But really any place that sells discounted tickets should sell tokens that could be exchanged for actual lift tickets at the resort.
But really the problem here is that an optimization — something that should never modify output or introduce random side effects — modified expected behavior.
Before you could ski with tomorrow's lift ticket in your wallet. Now you can't.