I've done much the same...
I had to go and support a user running an automated test system.
Looking at the parameters he'd given to the test in question, he'd just given the name of the parameter file - no extension, nothing.
"That needs to be a path spec", I told him.
So then we have a few minutes of him adopting his best patronising tone, telling me all about how that wasn't right, and this was just the body part of the parameter file name.
I let this run for a little while before mentioning that I had written not just this test, but most of the test tool he was using, and I was confident that this was indeed a path spec. I changed his parameter to a path spec and - shock horror - it all burst into life...