Yea, good old store and forward. We implemented it in our PoS system. Now, we do non PCI integrations so we arn't in PCI scope, but depending on the processor, it can come with some limitations. Like, you can do store and forward, but only up to X number of transactions. I think for one integration, it's 500-ish store wide (it uses a local gateway that store and forwards to the processors gateway). The other integration we have, its 250, but store and forward on device, per device.

I was shopping at a mall with a visa vanilla card once. I got it as a gift and didn't know the limit. No matter what I bought the card kept going -- and I never got a balance of what was on the card. Eventually, later that day it stopped. I called customer support and asked how much was left on the balance. They told me they had no idea my balance - but everything I bought was mine.

What I gather from this is to always try a dead card first just in case the store is in offline mode

I remember that banks will try to honor the transactions, even if the customer's balance/credit limit is exhausted. It doesn't apply only to some gift cards.