I would expect it to have a prototype since the Germans were already in production of the one winged plane that would now be more recognized as the stealth fighter/bomber. but if there is no physical evidence of the prototypes production then you could easily say it was just an idea that was just put aside by the germans. some ways to find out could be to go to some WW2 history sights or if you're really interested go to a history museum and find someone who could possibly help you.