It'll work fine but you may have to water a little more often than using a plastic pot. Nepenthes don't like wet feet though so it may actually be better for it. Get it out of the potting mix ASAP. It will kill the plant quickly unless it doesn't contain fertilizer as most do. Try to disturb the roots as little as possible. Dipping it in a bowl with water is a good way to rinse the existing soil off without much disturbance.

I have one of my nepenthes growing in a coco-fiber basket similar to a sphagnum moss basket and it seems to be doing well, so a sphagnum basket should be fine.