I keep an empty Disney gift card registered in my account! That way if one gets lost I can immediately transfer the balance to the empty card. While on my trip to Disney I give the empty registered card as well as additional unregistered, empty cards to someone else in my family in case I lose the $$$$ cards. So, if I have 4 loaded Disney gift cards, I also bring 4 empty Disney gift cards, that way each loaded card has an empty backup.
Stay with me, here's my logic: I have 4 full cards registered containing all my vacation funds and 1 empty card registered for transfer purposes. I lose 1 card: I can immediately transfer the funds onto the empty card. If I loose all 4 cards: I can transfer 1 card to the empty registered card, delete missing card #1, register empty card #2, transfer funds from missing card #2, delete missing card #2, and so forth. This way I have the ability on my trip to transfer all vacation funds to new cards if necessary. A bit paranoid I know but hey, I lose things all the time and this is something I literally can't afford to lose!