New ask Hacker News story: How to respond when close friends are using my idea in an incubator?

How to respond when close friends are using my idea in an incubator?
3 by recyclable_user | 2 comments on Hacker News.
Forewarning: I am going to keep this relatively vague and detail sparse. I do not want to blow up my colleagues' spot and I am looking more for interpersonal/professional advice in how to broach the topic with them directly as friends, without bringing in outside influences. Last year, I was discussing ideas with a set of friends. I brought up an idea am confident I originated (at least within the context of the discussion). At the time, two of those friends were workshopping a startup in an entirely different domain. A few weeks ago, I found out that my friends had been accepted to an incubator with a prospective idea that, though not the entirety of what I had discussed, was essentially the business proposition/revenue generating portion of my idea, by itself. Upon hearing their idea, my first thought was "didn't I tell you exactly this idea?" but I played it cool and did not bring up that I had originated this idea prior nor that I discussed it with them in presumed confidence. I would like to meet with them in person to broach the topic but I don't know exactly how I should do that. The relationship between me and these others makes me believe that they were not acting out of malice or trying to swoop the idea from me, but maybe genuinely thought they'd arrived on this idea on their own. I know from my own memory that often things can pop out that you think you came up with that in reality you lifted wholesale from elsewhere. That said, I know from notes I kept long before the meeting that I had this idea before discussing it with them and that I did not come to it mutually through that discussion. I have no belief that I could compel them to stop and I am not sure that that is my goal in the first place. More so, I am hurt as a friend and a colleague that they would take the idea without credit or forewarning and I feel I must broach the subject as a matter of personal principle. I have not had experience with such a situation before and would appreciate any ideas that the HN community is willing to provide.