I'm a friend of Luma Party as well. I remember talking to him all the time through PMs (Personal Messages) and chatting back and forth in both of our profiles. His disappearance came abrupt last year, but the reasoning behind that is completely unknown. I have no clue why he quit coming on. Given that you are the sibling of Luma Party, I thought you would know the cause, but it appears he kept his disappearance all to himself. Don't know why he stopped playing video games, and speaking of which, he also stopped being my friend on Nintendo platforms (3DS/Wii U). I guess he must have removed his Nintendo Network account, as there are no traces of him.