Even in the worst possible scenario at least one of the 4 remaining edges is actually in place. Find that piece and rotate the cube until it is positioned in the Front as shown below. If you perform the following move, you will be able to put all 4 pieces in their correct locations.
Note: You may have to perform this step twice to get them all in place.
All pieces are now in place, in fact you may actually be done now. Your cube can now only appear in one of 2 different states. I have outlined those states below with the needed moves to correct them.
The Fish Pattern
The 'H' Pattern