I have experience on it. When we attend a hackathon we have a fantastic idea and i am the presenter but already we checked there are some ideas near to us. but our one is specific and unique. Suddenly before our presentation other team pitch our ideas nearly fully( they didn't have that specific point before come to that place) but we never give up and present well and funny.

There's no matter your one is steal or copied but if you have well practiced and confidence you'll always unique than others.