If you're using Square/Stripe they should just be using Apple Pay anyways it's more secure. If the consumer doesn't have or understand that option I'd recommend they pull up the card number in the app. I use an online-only bank and with my phone and laptop in my pockets it'd probably take me about the same amount of time to pull out a credit card as it would to open my bank app with TouchID.

I had a card that won't swipe pretty frequently, after having to have my number typed or to produce a new card for the 3rd time I finally just reported mine broken and a new one was overnighted to me.

I've always thought that its the customers burden to produce a working payment method. If I got skipped in line because my card didn't work I'd have no problems letting someone else go ahead of me while I fumbled around with my phone and wallet.