yea I have been the victim of this too. In Indiana I didn't make sinkers. You can't sell a 1 pound sinker to anyone in Indiana. So most of the time I made spinnerbaits, buzzbaits, jigs, crappie jigs, etc. I was experimenting with a flexible leader wire instead of a wire shaft for a spinnerbait. I fished with a guy that was really interested in the bait. The problem I had was the leader wire coming out of leader connector sleeve and loosing the blades. Guess what happened a few months later? The Limberneck was a big hit. Even used the guys name on it...he was in the back of the boat with me that day. I never talked to him again.
Other lure that I was messing around with was a weedless bass jig with a flexible wire coming out of it just in front of the weedguard. I poured the jig with the wire coming out and the mold wouldn't close (since there was no spin jig mold at that time.) I was fishing a BASS tourney and got partnered with a big time pro. I used the lure and was doing well (I finished in the money.) The pro asked me about it and I told him a little about it. Then the next season of Bassmasters TV show, here he is using my lure to catch fish (this was the first Bassmasters show that shoed them fishing and was not a tourney.) Problem was that he called it a Spin jig from so and so company.
The lure industry is tough. Your ideas will be stolen if given an opportunity. It is kinda like the Wld West any more. I can't imagine how tough it is now, when I was doing my lure stuff in Indiana was 1985-1990. Then I gave up tourneys and went back to creek smallmouth fishing.