Truthfully no one abuses in public, so that information would really only be known within the home. It isn’t likely that people in the neighborhood would know this.
As far as answering my own questions, I personally never called anyone for information without introducing myself and letting them know something about my child and what I was looking for. I also told them how I got their name and how I was connected to that person so they understood the sheichus. If the person didn’t want to tell me something but knew who gave me their name, they could always call that person that did know them and speak honestly with them and let them decide what to do.
Lets say someone called me, introduced herself to me and said she was a friend of my sister’s. I might not divulge anything to her, but I might call my sister and ask how close she is with this person and what they are like and what they are looking for. If she tells me she is a neighbor of hers or she is very close with her and she is a forgiving person and can look away from certain things I might tell my sister to tell her to call me back. If she says she is close to her and was looking for perfection I might tell my sister to tell her the shidduch is not for her and I am not going to go into details.
But I am not going to divulge information to strangers who might make more of it than it is and might spread rumors on the person and make it even more difficult for them to get the proper shidduch. I don’t have the RIGHT to do that. I also don’t need to make enemies in my own neighborhood if this stranger tells the shadchan that I said this and that about the prospect. I don’t have to risk the prospect’s reputation for a stranger. On the other hand, if that person called the prospect’s RAV, they might set up an appointment to speak in private and might be able to give over information and not make it sound so terrible if it really is not shayach to effect the marriage, or he might want to meet the parents and explain what the situation is but tell them in such a way that he is reassured that they won’t be going around spreading the information. The Rav might want to find out who the Shadchan is and actually call the shadchan to find out what she actually knows about the prospect and the issues involved. A Rav certainly should know how to handle the situation better. If the Rav calls the shadchan his question would be why did you redt this shidduch, why do you think this is a match? How well do you know the prospects involved? I think that would be the best thing possible.