Hi Cyndrie, welcome back to planDisney!
A rainy day at Walt Disney World Resort is better than a sunny day elsewhere, but a sick day isn't fun anywhere. I'm sorry to hear you've been feeling under the weather; I'm sure Rapunzel won't mind us borrowing her Healing Incantation for a few lines:
Heal what has been hurt
Change the Fates' design
Save what has been lost
Bring back what once was mine.
Generally speaking, date-based tickets can be modified before midnight EST of the day before the ticket's first use date. I changed the date of a one-day EPCOT ticket last month by clicking the "Change Ticket" icon associated with that ticket in the My Disney Experience mobile app (three small lines at the bottom right of the app's homepage > Tickets and Passes). I then clicked the pencil icon next to the "Valid Ticket Dates" change option and selected my new desired date from the calendar. For dates with higher ticket prices, the additional cost was listed. Modifying the date of my one-day ticket automagically modified my theme park reservation, as well.
I realize the sun over Journey of Water has set on your ticket's original expiration date, Cyndrie. If you weren't able to change your original ticket date in time, the good news is your investment has no expiration date. The amount of money you paid for your unused, expired ticket can be applied towards the purchase of a new ticket. To make this happen, reach out to a helpful Cast Member at the Existing Tickets number. Make sure you have the ticket number from your unused ticket handy. If your ticket has already disappeared from your My Disney Experience account, you can find your ticket number in your original purchase confirmation email.
I'm sending loads of healing thoughts and pixie dust your way, Cyndrie. I'm going to go into "Mom Mode" and remind you to drink lots of fluids and get plenty of rest. You'll need lots of energy to save the galaxy on Guardians of the Galaxy: Cosmic Rewind and walk/eat/drink around EPCOT's World Showcase.
If you need help making plans for your new EPCOT date, Cyndrie, be sure to planDisney.
Jennifer