Every time I've looked at the map, I've always assumed the Silverwood was to the north of Rivenblight and there was a vast, unnamed forest of approximately the same size to the south of Rivenblight.
How much of your adventure depends on the Faerie Woods being in "The Silverwood", Patlin? Unless that huge tract of land in between the north and south halves was once forest, it doesn't make sense for cartographers to treat the two forests as one. Maybe it was cut down by men? Or maybe the catastrophe that destroyed Rivenblight severed the forest in two?