if you purchased the ticket online, you can just show the barcode in your phone to the scanner in front of every attraction, and no need the Disney pass anymore then.
Go to the ticket booth outside of the Disney entrance and they will replace it and cancel the other one. Besides, no one can use it as it has your photo.
if you are inside Disney they take a picture for the first time and that's enough to give you the tickets again
If you lost your pass in disney then go to citizens something or other in hollywood which is right after the motor car souvenir shop. If you lost it outside of the park, bring a proof of purchase to the ticket master at the front and they will give you a new one. I would suggest taking a picture of the bar code just in case, it makes both of these options go faster
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