Of course the lead developer waved you off. You wondered why things took forever, and the lead developer knew it was a complicated system and figured it wasn't worth their time investigating. It happened to be incorrect, but the lead developer wasn't in denial. They just filtered the issue out because they can't afford to go down every rabbit-hole they come across. I'm sure once you found the actual bug, it was later fixed.
The person I was responding to seems to think a large number of people are in denial when a bug is filed against them. That doesn't make sense, and isn't something I see. It'd be as if when you pointed out the actual bug, the lead developer continued to say it wasn't actually a bug (which is of course ridiculous and I bet didn't happen).