Is there a method to transpose specific pilot holes?
cut the head off of two bolts or nails that fit snugly into the holes, and extend out from the drywall some amount - may 1/4".  Line up the board over these pegs, and hit the surface of the board with a mallet over each peg.  This will make an indent on the back surface that you can drill.  Be careful that your first hit doesn't mess up your alignment for the second one.