Hi, So sorry to hear this happened to you....If it's a felt tip or sharpee you are plumb out of luck but if it's from a ball point pen...you may have a good chance...of rescue effort success.
Ball point ink must be removed promptly within the first 48hrs preferably within the first couple of hours...Try a soft white (art or pencil or pen )eraser first see how much you can get off...Try not to rub to hard or you'll lose orange color as well...
There are also ink killers or ink removers but they are quite harsh and you will lose the orange color below when you use them and then you'll have to redye the area...Hermes Orange is a very hard color to match...so I would not advise this route...Good luck...
If all else fails you can always just dye the belt black and cover the problem...and then buy another orange belt to cheer you up.Hugs, doc