Lee spent the night of October 19, 2007 with friends. He was dropped off at the friend's home in Buffalo Grove, Illinois at 10:00 a.m. the next morning and said he was going to the clothing store where he worked part-time. He was scheduled to start work at noon, but he never arrived there and has never been heard from again. On October 21, Lee's locked 2007 Toyota Corolla was found parked at a rest stop near the bluffs east of Baraboo, Wisconsin, along the Baraboo River. This area is nearly 200 miles from Lee's home. He enjoys hiking and camping and had visited this area at least once before, but his loved ones do not know why he would have gone there again. Inside the vehicle was a receipt from Kettle Moraine State Forest, printed at 1:41 p.m. on October 20.

Searchers found Lee's backpack and some of of his blankets were found near the Baraboo River. Lee's pants, containing his wallet, identification, some cash and his car keys, were partially submerged in the river. Among the item located were an empty bottle of an over-the-counter pain medication and sleep aid; a copy of Into the Wild, a true story about a young man who went to seek adventure in the Alaskan wilderness and wound up dying there; and letters addressed to Lee's family and girlfriend. The notes did not specifically mention suicide, but in one letter to his mother, tucked into the Into the Wild book, Lee wrote "I'll finally get to sleep" and apologized for "being a coward." The extensive search turned up no sign of Lee himself, and investigators stopped looking and announced they were certain he was not in the area.

At the time he went missing, Lee was a senior at Adlai E. Stevenson High School. When he was a freshman, he became depressed after he broke up with his girlfriend, but after receiving psychiatric treatment he appeared to make a full recovery. He was a good student, active in his Jewish faith, and the leader of the Jewish youth group B'Nai B'Rith. He was uncertain as to what he would do after graduating high school, but was considering moving to Israel or attending college overseas. Although there is no evidence of foul play in his disappearance, it's uncharacteristic of him to leave without warning and his family fears for his safety. His case remains unsolved.