Talk to them tomorrow and say “In the meeting yesterday, I felt surprised when you brought up idea X as your idea because I recall coming up with it myself. I was disappointed because I felt like you should have acknowledged my role in coming up with this. What are your thoughts?”

Their response to this should tell you whether it was an innocent mistake or them actually trying to take credit for your idea. If the former, then you’re all good - use this as an opportunity to build more relationship with them. If the latter, make it clear that you don’t want it to happen again, and know to watch out for them in the future.