The high school which I graduated from tells graduates to inform the school of their contact information all the time. However, some graduates fail to do it and become unable to be reached. They can't get the official organ of the school and invitation letters of alumni meetings or events like that.
The other day, I found one of my classmates who had been missing for 30 years by chance on the net. I was really surprised and had a contact with him. Additionally, more luckily, he had a chance to come back home through his business and we had a party.
contact information 連絡先
organ (フォーマル) (政府・政党などの) 機関紙［誌］
the official organ of the Communist Party 共産党の公式の機関誌
by chance 偶然に, 思いがけず