Tang was last seen at approximatley 8:00 a.m. on November 29, 2005 at his residence in the vicinity of the 700 block of Ashbury Street in San Francisco, California. His wife last spoke to him on the phone at 10:00 a.m. that same day. Tang apparently logged off his computer and left his apartment about an hour and a half later, at 11:30 a.m. He has never been heard from again.

Tang was probably carrying his cellular phone at the time of his disappearance, but it has not been used since he went missing, and neither have his credit cards or automated teller machine (ATM) card. He was carrying his wallet, keys and $80 in cash with him when he was last seen. Tang is married and has two young children. At the time of his disappearance, he was feeling depressed and was stressed from his job. He called in sick on the day he went missing. Tang disliked taking his anti-seizure medication, as it made him feel disoriented, and as a result, sometimes he did not take it as directed.

It is uncharacteristic of Tang to be out of touch with his family. His loved ones believe he may be homeless and is possibly suffering from amnesia. There were several unconfirmed sightings of him in the San Francisco area in the days after his disappearance. It is possible that Tang could be in Boston, Massachusetts; he was born in Massachusetts, graduated from Framingham North High School in 1983, and later attended the University of Pennsylvania. His case remains unsolved.