Help with saving block Locations and BlockData

So I am working on a plugin that makes some technical stuff easier to do in minecraft. The goal of the plugin is going to be that it will function something like gnembon's carpet mod. So I have gotten a lot of features in but I have some problems. What I do is I generate a hollow sphere at the players origin, I then save the locations of each block and their corresponding BlockData so I later on can remove the sphere. I use
sendBlockChange to send blocks to a certain player only (because they should only be able to see the sphere). I can generate the sphere, save the locations and BlockData, but when I try to load another sphere with that data to remove it it seems to have no effect. Any help is aprechiated

Here is the code of the process:

Code:

List<Location> SavedBlockLocation = new ArrayList<Location>();
List<Material> SavedBlockData = new ArrayList<Material>();

if (command.getName().equalsIgnoreCase("despawnzone")) {
       for (Location l : generateSphere(player, player.getLocation(),30 , true)) {
              SavedBlockLocation.add(player.getWorld().getBlockAt(l).getLocation());
              SavedBlockData.add(player.getWorld().getBlockAt(l).getType());
              player.sendBlockChange(l, Material.RED_STAINED_GLASS.createBlockData());
        }
}

if (command.getName().equalsIgnoreCase("despawnzone_stop")) {
        int count = 0;
        for (Location i : SavedBlockLocation) {
               try {
                    player.sendBlockChange(i, SavedBlockData.get(count).createBlockData());
                    count++;
               } catch (Exception e) {
                     player.sendMessage(e.toString());
              }
      }
}

generateSphere returns a List of locations where the blocks should be placed.