You'd think any SeriousBusiness would have a backup way to take customers' money. This is the one thing you always want to be able to do: accept payment. If they made it so they can't do that, they deserve the hit to their revenue. People should just walk out of the store with the goods if they're not being charged.
Why doesn't someone in the store at least have one of those manual kachunk-kachunk carbon copy card readers in the back that they can resuscitate for a few days until the technology is turned back on? Did they throw them all away?