Small patch of hair won't grow back after I shaved it. What can I do?

So a few years ago I accidentally shaved a small patch of hair right where my hairline is and has not grown back. My question is will it ever grow back? And if not is there any products I can use to make it grow back. Its a small area and can't really tell but I like my hair very short and when hairline is fully exposed its quite noticeable.