So sorry this happened, I know that can be gutting to lose. One thing I know many of us do is to purchase physical DGCs from
DisneyStore or sometimes in person at the parks. These gift cards usually have a scannable code (qr code?) on the back that can be scanned rather than swiped, which I like because you can also use that scannable code to scan the gift card for mobile order.
Then I usually try to buy all electronic DGCs at a discount and combine them onto one of the physical gift cards or if I have to buy physical cards, I manually combine or transfer onto one of the scannable code physical cards.
I know hindsight is 20/20, but I also take all of the card numbers for the physical cards and put them into my password vault. So if I ever lose a card (its happened to me before), I can use the DGC website to move the funds off of the card and onto a different card.
Its feasible the card fell out somewhere that nobody else could pick up, like on a ride or something - so maybe when you get home you'll be able to get the card number and move the funds onto another card.