It sounds like you are very worried, but keep in mind that a few days doesn’t necessarily mean anything. Freelancers work weird hours, have other obligations, and sometimes people are just not great communicators—any of these things could be the reason for radio silence. While you can’t go back in time and have him sign an NDA, you could still put something in place since it sounds like you are very concerned about protecting your idea (and rightfully so). Since you can’t legally protect an idea with any sort of copyright or patent, you could set up a contract for the freelancer to sign ASAP.
If I were you, I’d get in touch with an attorney to help you set up an airtight contract. Continue to reach out the freelancer and hopefully he will respond soon. An attorney may also be able to provide further assistance about your potential options if the freelancer decides to do something less-than-honest with your work.
is happy to connect you with a qualified attorney. We offer affordable rates and flexible communication so that we can better serve you. Check out our website and please do get in touch if you think we can help. Good luck!