The missing scale could be from rubbing or getting caught on something ... it won't grow back. The red areas are a bit concerning if the bite happened a month and a half ago. Do you have a picture of the snake? Mine with an infected mouse bite was on the white part of her neck (she is a pied) and it's only a bit pinkish. The bite was recent and my Vet isn't concerned (I was there for another reason). If you have a dark snake and it's noticeably red, I would bite the bullet and pay the $40-60 exam fee rather than something much more expensive or a loss later.