Hi. Somehow knowing the name will help in your healing and closure. To still be obsessing over the name to me means that you are still struggling with what happened. Doesn't the college have records which could help you find this name? or are there any other people you were friends or people who would remember? Go to the police and file a report even though it happened 20 years ago or ask someone how to go about it? Hey in Australia where I'm from there are Catholic Priests getting done for sexual abuse that happened more than 20 years ago so what's the difference? Best of luck