This happened to me. It actually started with, "I accidentally told this wifi router salesman guy at a trade show that I would listen to his sales pitch. Now he's coming to our office in an hour to give it. Can you sit in on the meeting with me so I'm not alone? You know a lot about wifi, right?"

I didn't even know what the meeting was about. I assumed he was trying to sell our office a wifi mesh system, which we already had. It wasn't until about halfway through that I realized that he was trying to sell us these routers+source code so we could integrate them into our product line and resell them. And then I realized how many of our problems that would solve, so I started asking questions. Next thing I knew, I was the lead engineer on a wifi mesh system.

It was a super fun project, though. And I got lots of raises and a title increase for taking it on.