Omg that sucks!! Im so sorry
It sounds like its pretty limited... but you can take this time to do some bonding and ground manner work with your horse :) even though its basic stuff, it helps all levels of riders and horses to go over the basics every once in awhile. Also, maybe try and teach your horse a different type of riding to keep him interested- work on dressage or western pleasure or something... idk but basically change it up!!! Your situation is horrible, but since theres nothing you can do about it you might as well take advantage of it in any way you can