Solved How do I deal with a OfflinePlayer?

So I am making a plugin and I am getting stuck at one point. Im creating a MiniGame plugin and i want to add a /rejoin command. This command is used when the player leaves the server and comes back on and wants to rejoin the game they were in. That part is not going well. It keeps sending the message to the player that i coded that says they were not in a game when they left. I created a HashMap like this to store the players once they left: ... = new HashMap<Player, (mygameclassinstance)>();
I realize now I should have used OfflinePlayer as they are put into this Map when they leave the server. Does anybody know how i would deal with it if i were to do ... = new HashMap<OfflinePlayer, (gameinstance)>(); ? I mean as in then when a player joins back on the server and rejoins, they can do /rejoin and then it will somehow make a offline player go to a player. Also this vice versa from a Player to OfflinePlayer, I think its something like p.getPlayer() which returns their offlineplayer variable, im not sure about that tho!

Im not sure i have tried this from looking at the methods in the player and offlineplayer:

Code:

 

//Creating a offline from a online
OfflinePlayer off = someonlineplayer.getPlayer();
//Creating a online from a offline
Player on = someofflineplayer.getPlayer();

That does not work. Any idea around this?

 

Goooooooood point wow thanks @timtower yet again lol