Hi there, Rachel!
Oh, I hope you can still find a way to use that remaining day of your
Southern California Residents 3-Day, Weekday Ticket. The availability of
theme park reservations can vary. Even when a date appears to no longer have reservations, they do pop up once in a while. I was watching the
theme park reservation availability calendar early yesterday and did not see reservations for today. But later in the evening, I did see Disneyland Park become available. I recommend refreshing that calendar frequently to see if openings show up.
Whether or not you use the last day of your ticket, you may still use the amount you paid for your current ticket toward the price of a
Disneyland Resort Magic Key pass. You may
upgrade a theme park ticket to a Magic Key pass within the
Disneyland mobile app. This process must be done by midnight of the last day you use your ticket (if you make a reservation for that final day) or by the expiration date of the ticket, May 26, 2022, whichever comes first. The ticket purchase price becomes the down payment on the new pass. And as a California resident, you are eligible to pay for the remaining balance in monthly installments.
I hope you have a magical time at the Disneyland Resort. See ya real soon, Rachel!
~Tony