I was surprised and angered (since "my" idea had been stolen)

My feelings are the opposite. I become exceedingly pleased and amused to find that someone else did it first. Aside from it being instant vindication, it just makes me happy. I feel a sense of kinship knowing that someone, somewhere, had the same data I had and came to the same exact logical leap that I did. It's like we're research buddies across time.

Though I do feel silly and a little mad at myself when I've wasted a lot of time synthesizing something could have just researched instead.