There are no "buts" in a vendor - customer relationship. The vendor was completely at fault in this instance; the customer was completely right (in following rules, setting up a winning trade and placing said trades in the TT system). There are business "ethics" in a free, capitalist society. Caveat Emptor does NOT apply in any regulated, brokerage environment. If it currently does, then there needs to be "change".
No matter what some "words" on a piece of paper say, TT is a fiduciary ! It may be a fiduciary for only a tenth of a second a few times a day, but TT ~ is ~ imo.
The customer was harmed, the customer did no wrong, matter of fact, the customer, taking on their own responsibility for their own actions, alerted TT of the problem. Who knows how many other clients would have been harmed if the client didn't alert TT. If TT was an ethical partner and vendor, the client would have been made "whole" immediately and a credit for 3x the damage to his account should have been credited to his account the following day. That is "ethics"...and taking care of clients when your vendor wrongs them is what mature, ethical businessmen do.. That has been the way things have been operating since the Magna Carta ...don't settle for less people.