Well, what exactly do you mean by 'disappeared?'I'd check census records, death records, the SSDI. If I had more details, I'd have a better idea of what records would be the most promising. If you know where he/she was last seen then you could serch that areas death and medical records to find a bit of info.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.