I believe you have the RIGHT to request an erroneous trade review. There may be a fee involved. But the broker should not refuse you, especially in an extreme case like this.
Actually, best case scenario is that the broker failed to contact the exchange. That is clear negligence, and regardless of the merits of the claim, and gives a good chance of recovery. The paper trail on this is trivial, he called them after a trade that any jury (which is important because of the preponderance burden) would recognize as not clear intent. If the broker did not follow up in good faith (fiduciary duty) and document it in its entirety, it's game, set, match. They denied him the opportunity...good help them is they cannot produce a complete record 100% in agreement with those supplied by OP's third party vendors (I.e. Email provider, phone provider, etc.) They may have a supplemental claim against a third party, but that's beyond OP...worst they could do at that point is subpoena him to a deposition to verify their version is events. I suspect this isn't the case, but makes it very simple from a fiduciary liability standpoint.
I sent a letter of complaint to my broker last Friday. I'm waiting for an answer. Of course, I'll let you know the outcome. Here in Montreal, a letter like that is the first step that we're supposed to do. I'm hoping that they will realize that they didn't do what they should have done. That trade should have been cancelled within' 30 minutes after the trade but they called ARCA only the morning after.
The system needs to be equitable. Why would the other 1000 share order be busted, but yours not? Either the other order went through a broker that had more experience with these issues and handled it expeditiously. Or the other trader had more influence, i.e., unlevel playing field.
I think that the fact that the other 1000 shares were busted is certainly helping me. There is no way that they can argue that it wasn't possible to do it.
Do you have any hotkeys you may not be aware of that can change the price in $10 increments? Also, sometimes when I place an order I accidentally move the mouse scroll and that changes the volume of my order.