With a saw you almost certainly will injure your snake. You'd probably be better off with a hammer and chisel. What you would be doing is finding a spot that is open space further up the side, placing the chisel there and striking it with a hammer to create a small crack (don't worry if you don't see a crack). Then continue to tap a line down to the hide opening, and back from the intital strike down to the hide opening.
You wouldn't want to be hitting the chisel hard enough to punch through, just hard enough to be tapping a crack into place. Your hand holds the chisel to provent it from traveling too far and going inside the hide.
Still, try scenting first, and even then give it a day before chiseling (hopefully it won't be in feeding mode when you free it if it is trapped)
Keep in mind that however you try freeing your snake, you could easily kill it or injure it. That's why I suggest scenting. Personally I'd dremel the snake out with one of the circular grinding/cutting wheels. Essentially etching a line around, then tap the line with a flathead screwdriver and hammer. However I am fairly good with a dremel, and wouldn't be worried about cutting through and into the snake.