I guess this question is probably more about how the concept of "theory" exist if a particular theory cannot be proven.
How does people who form a theory know that this thing will do this or that thing exist if they cannot prove it?
For example how does the theory of dark matter/energy or string theory come about if it cannot be proven? Did something hint people to their possible existence but they just couldnt prove it?
Another example would be gravity. I guess before it was theorized people were already experiencing the phenomenon of things falling down but it was so intertwined with how the world works that it was just a natural phenomenon.