UUID Set and Retrieve

//UUID Set
public boolean itemInteractionForEntity(ItemStack stack, EntityPlayer playerIn, EntityLivingBase target) {
    if (target instanceof EntityWorker && !playerIn.worldObj.isRemote){
        NBTTagCompound tag = new NBTTagCompound();
        UUID id = target.getPersistentID();
        playerIn.addChatComponentMessage(new ChatComponentText("ID: " + id));
        tag.setString("id",id.toString());
        stack.setTagCompound(tag);
    }
    return super.itemInteractionForEntity(stack, playerIn, target);
}

//UUID Retrieved
public boolean onItemUseFirst(ItemStack stack, EntityPlayer player, World world, BlockPos pos, EnumFacing side, float hitX, float hitY, float hitZ) {
    if (player.isSneaking()) {
        // ...
    } else {
        NBTTagCompound tag = stack.getTagCompound();
        if (tag!=null){
            if (tag.hasKey("id")) {
                String idStr = tag.getString("id");
                UUID id = UUID.fromString(idStr);
                // doesn't even get here ...
            }
        }
    }
    return super.onItemUseFirst(stack, player, world, pos, side, hitX, hitY, hitZ);
}