Oystercard - the problem is when the man meets the machine

I had my first practical unsatisfactory Oystercard experience today. I tried to get the 212 bus (franchise holder First) to Walthamstow Central this morning, and the card would not swipe on the bus driver's ticket machine. As I walked away there was a tap on the plastic grill that separates the driver from the public. I told him that the card didn't expire until next week. I tried the card another couple of times. It didn't read. He wasn't rude, but he insisted that I paid a cash fare for my journey. The card was valid and I used it fine at every other stage of my journey, so it looks to me like the fault was with the card-reader on the bus.

As with most technological systems, it is usually the interface with the humans that causes the problems. The bus driver was obviously getting no feedback that the reader wasn't working. Or hadn't been trained to understand it. I hadn't thought to carry print-outs of the emails that confirm the purchase of the ticket and the successful download of the ticket onto the card. And the Oystercard website doesn't have a clear route for claiming a refund when you've had to pay a cash fare because there has been an equipment failure, although I have emailed them...