Most listing agents on REO properties do not represent buyers as well and will refer you to someone else in their office. Whatever the buyer's agent stated would be hearsay without proof. Maybe if you asked him to e-mail you his proposal and the advantage to using him, you would have documentation to present for someone to review for violations to our association of realtors, or California DRE guidelines. As it is, there isn't much to go on.

While I don't doubt he said what you described, we can only speculate on how the 'winning' buyer was selected. The listing agent may have not influence on the final selection. Most asset managers make that decision, assuming all offers are submitted as expected. I guess you can get a better idea once the purchase closes since the selling agent, the price of the property, etc. becomes public information.

Any impropriety can then be brought forward...but of course it's too late for you to acquire that particular property..

As others have suggested, the best choice is to work with a strong buyer's agent to negotiate on your behalf. There's no guarantees but it increases your odds.

Hope that helps, and hang in there...

This is a situation that your real estate agent might need to report to his local board...better yet roll up his sleeves get on the phone and demand answers as to why your offer goes from "looking strong if you use me" to no deal when you don't. I am not familiar with the particular rules of your state but in New York that could be interpreted as a tie-in-arrangement which is obviously illegal.

Why do you call the listing agent, if you have a broker?
Doing so you might have given the impression that you didn't have anyone representing you... or at least, not someone that takes good care of you.
While the partner sounds like he could have helped get your offer accepted, it would have been a dual agency, where in essence, you agree to not have buyer's representation (since both agents are working for the seller).

On the surface something does look fishy. If there is a real and documented advantage to working with a particular broker on a property, such as a lesser commission, it must be advertised in the MLS so all agents can see what they are competing with. When you indicate you have submitted several offers I assume you have a local agent/broker representing you. If you are talking about a Loan Broker, that is something else. Their relationship with the listing company must be disclosed in writing. You cannot be forced to use any Broker; however, you can be required to be pre approved through a loan broker that the listing agent has confidence in. This weeds out the cursory pre approvals which may not be worth the paper they are written on. My advice it for you and your agent to personally confront the lsitng broker and get to the bottom of this, especially if this listing company lists a lot of the properties in your area.