I interviewed with a series B company a couple of months ago. During the interview with the CTO I proposed a way that could effectively 3X their MAU. They were genuinely impressed by it, and stated they didn't think of that. Like it seemed natural, and I'm considered an expert in this field.
I ended up not getting the job, and not thinking much of it. Fast-forward a couple of months, and it's their new growth strategy. I got no credit for this, and not even a call back. Is there anything I can do?
To turn an idea into property you have to take out a patent. Then you have property. Usually ideas are not patentable because they've been done before.
I sympathize with you not getting the job, but don't worry, you'll have other ideas.
Ideas in themselves have no value. The ability to have ideas is good. So instead take this as encouragement and move on to the next idea.