There is a 3 day FL res ticket usually, not sure why they didn't look for that? Typically with the savings offered for FL resident tickets, there is no way to roll over any "money" as the tickets are usually significantly discounted from an original 4 day ticket price already. Disney tickets are now all "use it or lose it" with the non-expiring option a thing of the past sadly.
Now, if there is still time left on their usage period for the ticket, they could look to make a reservation and use the day in the future. The ticket rules vary based on the sale. Sometimes its "all days must be used within a 14 day period" sometimes its "Come any days in this 6 months minus blockouts for holidays". It really does vary based on what kind of FL resident ticket they purchased.