"Was the F16 in contact with approach? Was the traffic called? Was the Cessna in contact with approach. We all know see and avoid can be difficult, esp. with fast airplanes. Some problems are unavoidable and the fickle finger of fate intervenes."
The F16 was shooting approaches into Charleston on a IFR plan, so he was "heads down" and talking to ATC. The 150 was departing a satellite airport just outside of the Class C shelf and was legally not talking to anyone, nor was he required to. The 150 was probably in a left hand climbing turn.
My guess is that it happened too quickly for ATC to see the C150 pop up on radar.