Sinisgalli was last seen by his family at Jerry Ivey Park in south Salina, Kansas on August 17th, 1987. His wife saw him driving east on his way home from work at Beech Aircraft Corporation in Wichita, Kansas. She followed him to the park. He stopped near the restrooms and spoke to her. He was surprised to see her and told her he was not feeling well. He had drunk a pint of vodka on the day of his disappearance. Sinisgalli's wife tried to convince him to let her drive him home, but he refused. She left him to get help from her brother. When Sinisgalli's wife returned to the park, Sinisgalli was gone. His car was still parked by the restrooms, locked, with all his belongings, including his lunch box, inside. He did not show up for work the next day and has never been heard from again.

Since Sinisgalli's disappearance, he has not used his Social Security number, credit card or bank accounts and he has not contacted any of his family. He was devoted to his two children and it is uncharacteristic of him to leave without warning. He is originally from New York, where his parents, who are Italian immigrants, live. He had been living in Salina for about nine years prior to his disappearance.

Sinisgalli's loved ones fear he became homeless. They distributed missing person fliers in New York and in Florida, where his sister lived, but he was never found. His case remains unsolved.