Well since you obviously can't put the gill back i would put salt in (like you did) and let it be. Until there are any signs of bacteria etc... And i would also try and find what happened. But if i were you for any reason at all i would have a hospital tank up and ready. Just in case. But polys are strong i personally don't think there is anything to worry about after it passes the 3-4 day mark and show no signs of struggling with it.