The answer to the question of "why did you dump me" is almost always answered with, "because I didnt want to be with you for some reason"
IF it was for some other reason, family trouble, no time, moving away - I think that would be clear and the person will probably tell you why. Then again, I once broke up with someone by telling him it was because I was moving away but the truth is I just didnt like him anymore.
anyway, if you dont know why someone dumped you, and they wont tell you why, I doubt you will get an answer to it on the internet. I do kind of sympathize, I always so want to know "why". But this seems a silly way to do it. Cant force someone to tell you the truth.