It sounds like Helen has an ear that is going to help solve this, if anything will.

any way to search the human voice within recordings? (I didn't clip the whole thing, because I'm a retired writer/marketer/web content editor from a library. Not a librarian, though I did a lot of that work before I finished. Go figure.)

I think the FBI might have software to do that; the rest of us have to search a bit harder.