The reservation is forfeited, not the ticket. Probably just legal stuff they HAD to include, because literally someone out there would probably ask Disney to invent time travel so they can go back and make their reservation, but it’s only the reservation itself that is forfeit. Your ticket will be fine to use for another day prior to its expiration date. And if it’s after the expiration date, Disney will generally let people pay the difference in ticket amount if prices went up in the interim and give them a new ticket.