No Record of My Employment

This is a fairly odd and confusing story but please try to stick with it.

I was an ER intern at Prop Trading Firm A. Prop trading Firm B was a partner in Prop Trading Firm B at the time of my employment but bought out the rest of the firm shortly after I stopped working there. Prop Trading Firm B has no record of my employment.

Evidence in my favor (I think):

1) A wire transfer from Prop Trading Firm B, while I was working at Prop Trading Firm A. I guess Prop Trading Firm A took care of payroll?

2) Published Research in my name on Seeking Alpha that also has Prop Trading Firm A’s name on it. Prop Trading Firm B decided to change the name of the account to something that has nothing to do with them or what was formerly known as Prop Trading Firm A. However, the disclosure still mentions Prop Trading Firm A and that cannot be changed.

3) I spoke with the former Managing Partner at Prop Trading Firm A and his team of guys have decided to start a private hedge fund. He said to tell anyone who needs record of my employment to call him directly.

I know most firms simply call HR to check for records of employment and I don’t want to get blacklisted because someone thinks I lied about my employment history. How do I go about this situation?