Gravity Sump Pit

I am not a professional so please excuse me if I use wrong wording! I have a sump pit in my house that I was told was gravity drained. I recently had water back up into the basement for the first time in 10 years. My main question is how is the gravity drain pipe connected to the system? I have two 4 inch French drain pipes that drain into the pit but I see no pipe to gravity drain. I have emptied the pit by manually scooping out the water so I can see the entire pit. Is it possible that a contractor would hook the gravity drain directly to the French drain somewhere? Any help as to my next step would be greatly appreciated!

 

I have never heard of a gravity sump pit. The pit usually exists to hold a pump. If the system is totally gravity the pipes simply run downhill until they empty out somewhere on the surface.