I competed in a Facebook hosted hackathon at my university and my team and I were able to create a product that won second place in the competition - and for discussion's sake lets call it AppX.
The feedback that we received for AppX was incredibly positive from the Facebook engineers that hosted the event so we decided to polish our idea and eventually release it to the public. A few months later (before we were able to release it) I read an article about a group of students from a different university who created a product that had the same name and functionality as ours.
I was pretty bummed out at the fact that we didn't release our product fast enough and that someone else just so happened to create an application just like AppX and that it had the same name and has recently been gaining a lot of publicity for it.
A day later after sharing the article I read, a classmate of mine who participated in the same facebook hackathon as I did (but was on a different team), had participated in another hackathon after the facebook one, and at that event she mentioned our AppX idea to her teammate. It turns out that the her former teammate is the founder of the application that has the same name and functionality as AppX.
What I want to ask is:
Does my team have any way to reclaim credit for our application if the idea was actually stolen?
I am not a lawyer but I can't imagine you have any recourse here. If you want to protect the name you need to trademark it. If you want to protect the idea you need to patent it.
If you have done neither of these I can't imagine you have any legal standing.
I would rename and launch your product. You have noticed that not launching yet has cost you... well don't let it cost you more, launch and compete. You had the original vision for it, hopefully you can deliver better than them on it.