First, just look at each WAV file, just in the hex editor. If everything shows up as 00s, your data really is lost. Assuming these aren't some special structure, the first 44 bytes describe the file. Everything after that is sound samples that are literally amplitude (loudness) values. A file that is 44.1 khz, 16 bit, stereo, each second of audio will be 176,400 bytes. A full minute would add up to 10 MB.
There's an existing grammar but, before you look at that, I'd recommend reading up a little on how a WAV file is structured:
The grammar for Hexinator / Synalize It! is called "Windows Wave" because the format was introduced by Microsoft. It's a slightly complex grammar but you could try using that and see if it can tell you anything useful. Of course, if you're bored or drunk and want to see something really complex. take a look at the MP3 grammar. You'll start to wonder how humanity has made it this far.