No I have not experienced or heard of this.

The only insight I may be able to give you is that teenagers are very vulnerable to sexual identity issues. I teach high school and often have students who are 'experimenting' on both sides of the fence. I believe it is for many reasons.

Experiencing a sexual trauma at this age, I believe could put anyone in a tailspin about their own beliefs and tendancies at that age. Maybe, if currently he feels unsure, he should persue these topics in therapy. This is a tough issue for both of you.

You should feel good that he was willing to share this with you. If it were me I don't know that I would be able to share it with anyone ever other than my therapist. Somewhere there is a reason he shared it with you. Let time take its course and unravel this slowly. Do not take his choices or behaviors personally because they are his issues, in my opinion.