I just looked that up. Pretty amazing, actually. It happened in 1983...Besides, we all know the record that the F-15 has - I distinctly remember reading a story where one lost its entire wing and still the pilot managed to get it on the ground, saying it just listed to one side and needed more throttle to stay airborne. I also saw that story on the History Channel. That's a good fighter.
The wings have three spars and the aircraft can still fly even if one of the spars has been shot away. The Eagle's outstanding aerodynamics allow it to stay in the air even with a loss of a substantial portion of a wing. In 1983, one Israeli F-15 actually lost all but a stub of one wing in a mid-air collision during training and managed to still land safely, to be repaired and returned to service. The wings of the prototypes had a slightly wider span than production machines.