ThanksInteresting question. I had a discussion with Jerry about this precise issue several years ago. If an individual begins to exhibit "homosexual" behaviors after a traumatic event (such as abuse) or after a failed relationship, I would question whether this was a reaction to distress because of the triggering issue. This could be nothing more than a set of symptoms of an actual psychological disorder... depression, PTSD, or some psychosexual disorder. If it was due to one of these diagnoses, I would NOT conclude anything about their sexual orientation until they received treatment for these issues. Is it possible that they really are homosexual? Yes. Is it possible that they are NOT and the behaviors that they exhibit are the result of actual distress caused by a psychiatric issue? Yes. First step would be to help the individual explore the triggering issue, THEN try to help them to determine their sexual orientation.
So, I guess the answer to your question is, no, I do not believe that a trauma like you mention can "change" one's sexual orientation. The "change" one might see is either a problematic reaction to the trauma, or the presentation of something that was hidden.