Hope you have good memory :)

Maybe you should have intermittently checked the recording device??

Well just go back. If the are old, you may be able to convince them that the first time never happened.

The good thing is you can prob re interview them, it's unlikely they'll remember you anyway....

As a researcher, that's something we know happens quite a lot: the batteries could die during the interview (even though you just put in new ones!), or somehow it just stops out of the blue. We usually take two of those recorders with us and set them up at the same time. But yes, someone had to go through that entire "I had a focus group interview for three hours and it didn't record anything"-phase as well in order for us to stop taking risks.

Just go back and redo the interview.. It's not like they'll remember the interview anyway... ;)

Always verify your equipment. Especially if it was important. At least you should have learned a lesson for the future.

Maybe you could ask them if they wouldn't mind doing a follow up interview? Good luck with your paper! I'm sure you'll figure it out =)

Depending on how elderly they were, you may be able to quickly go back and do the exact same thing again, and hope they don't remember

Sucks! Hope you were able to do well!