Well, if it happens again and you'd like to go to camp with a dead follower, there is another way to go to camp. Open the full map (M by default on the PC), not the mini map, and on the right side there's a panel named "Waypoints" with a list of fast travel locations. The top one is "camp" and that is how I always have to go to camp when I have a dead follower. Sorry my original explanation was unclear!
Even that didn't work for me once. Wyll's body completely disappeared, and there was no way I could get back to camp despite trying multiple methods. What finally worked was to save the game, and reload. Wyll's body was then right where it was supposed to be and I could hit it with a "Revivify" scroll.
