I think it has been completely answered above that you have not to expect any payment at all unless the site is generous enough to pay you , they did not ask you to find bug , actually this has happened before and the account that reported the bug did not received any amount so he needs to create a thread here but to reality , he received criticism for expecting payment when he wasn't even tasked to do that bug finding , and if you have found this accidentally then just let it out , or not act anything and just pretend this isn't happened .