Lange was last seen at the Wheat & Rye bar on Allen Road in Allen Park, Michigan between 11:00 and 11:30 p.m. on December 30, 2003. The location is across the street from his own place of work, Tulio's La Riviera Restaurant, where he was a cook; he went to the bar after finishing his shift at work. The last call Lange made on his cellular phone was at 12:30 a.m. on December 31. The phone went dead a few hours later and Lange has never been heard from again. His vehicle, a black 1999 Mercury Sable with Michigan license plates numbered XQS 481 and a large dent on the side, has not been found.

Authorities initially assumed Lange had personal problems and left of his own accord, but he is now believed to be in danger due to the length of time that has passed since his disappearance. He was the primary caregiver for his young son and it would be uncharacteristic of him to abandon the child. The circumstances surrounding Lange's disappearance remain unclear and his case is unsolved.