Please imagine that you have introduced a buyer and a seller to each other (both of them are your friends, but they have not been familiar with each other so far.) The two people have been connected to each other for a period of time after your introduction, but you are not aware what they do throughout this period of time, although you know that they are connected to each other at the time being.
After a while, they had a deal (i.e. one of them has sold an apartment to the other one.) But they have faced some financial problems with each other. One of them finds you guilty and he/she thinks that you shouldn't have introduced them to each other! Even that person thinks that somehow you have received some amount of money or advantage from the other person!
I need to know whether saying the following sentence (which we say in our language) works properly or not when you are going to say that what has happend was none of your business and it's their own problem, and you have no gain in this issue:
I'm not a beneficiary in this matter. [to me, this sentence sounds OK, but I have no idea if it makes sense to a native speaker too!]
If it is not natural, then I wonder if you could tell me what shall that person say to indicate that they are not a beneficiary in this matter?