It seems that this is a bug with the "Raise to listen" feature.
I have to admit, I was stumped when I read this thread yesterday until it happened to me today.
What happened was I set the phone down in my car seat and my leg covered the proximity sensor. When I moved my leg, I notice my screen lit up and there was that 0:00 second voice message like pictured.
I tried to recreate the issue, but I couldn't get it to do it. I'm still pretty sure Raise to Listen is somehow responsible, though.
You can disable it in settings>messages. Let me know if that fixed the problem!