Before Newton Named Gravity didnt mean it didnt exist, just call it whatever you like.
Before Newton gravity was still "detected" by people. You on the other hand just made up an undetectable force. Lots of things in science are based on theroy rather than proof. The problem is that if it becomes the accepted Therory it is taken as being proven.
Your problem is you're confusing "Scientific Theory" with "guessing", a scientific theory will always remain a scientific theory because it is an explanation of scientific facts.