Hi Nathan, and welcome to planDisney!
I am so sorry to hear that you got sick while enjoying a past
Walt Disney World Resort vacation. Even though it happened in 2015, it is still a memory that sticks with you, but hopefully, you will be creating new memories in the near future.
The good news is that all unexpired theme park tickets with the remaining admission days will be honored. However, because you do not have possession of the voucher, the best option would be to call 407-939-1289 to speak with a cast member to see if they can assist with your specific question. In addition, if you happen to be at Walt Disney World, you can always check with Guest Relations when you arrive at the theme park. I hope this helps.
Please return if you have additional questions.
Have a magical time!
Raquel