Bukkit

	public void barHideEvent(BarHideEvent event) {
        OfflinePlayer player = event.getOfflinePlayer();
        //more stuff, like restoring the tag of your plugin.
        }

package your.packege;

import org.bukkit.OfflinePlayer;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.plugin.java.JavaPlugin;

import com.gmail.filoghost.api.BarHideEvent; //the import

public class Main extends JavaPlugin implements Listener {

public void onEnable() {

//check if the plugin is loaded
if (getServer().getPluginManager().getPlugin("HealthBar") != null)
	getServer().getPluginManager().registerEvents(this, this);
}
	
public void onDisable() {}
	
@EventHandler
public void barHideEvent(BarHideEvent event) {
//you don't need the online player for scoreboards
OfflinePlayer player = event.getOfflinePlayer();

//prints the name of the player whose tag has been restored.
System.out.println(player.getName());

//more stuff
//...
//add the player to a team for example
}
	
}