Witwicky was last heard from on February 11, 2003, when he called his mother who lives in Florida. This was the same date that he last logged onto his computer. He has never been heard from again. In March of that year, he was discovered missing when the managers of Pinnacle Heights Apartments in the 7900 block of east Snyder Road in Tucson, Arizona, where he lived, requested a welfare check on him.

Witwicky's apartment was locked and appeared to be in order when investigators went inside. His vehicle, keys, wallet, cash and credit cards were left behind, but his handgun, spare key and and cellular phone were missing. Witwicky was self-employed as a computer consultant in 2003; he moved to Tucson from California two years prior to his disappearance. His case remains unsolved.