It's been a complete mystery since August 29, 2015. Elijah "Bear" Diaz, who was 20-years-old at the time, vanished without a trace from El Cajon, CA.

According to the San Diego Union Tribune, Lelaine Thompson dropped her son off on Joey Lane in El Cajon around 10 p.m. She says her son was severely ill from diabetes and he was not able to walk or drive on his own, that's why she transported him.

Only 24 hours after Thompson saw her son, and authorities were contacted, they found his cellphone. The phone was off and an investigation uncovered a 50-inch television from his bedroom was missing as well, reports add. Diaz's bedsheets and the contents of a safe were also gone.

Thompson said, “I believe that someone out there knows what happened. I believe there is hope for answers. I know we miss him. I know he was loved by many people."

At the time of his disappearance, Diaz stood 5 feet 9 inches tall and weighed 110 pounds. He has brown hair and brown eyes and was born on August 19, 1995.

Diaz has a tattoo of a bear claw on his left forearm and it's possible he could be in need or seek medical attention.

If you have any information about this case, please text the "In Pursuit with John Walsh" hotline 24/7: 833-378-3373 (PURSUIT)

Read more NCMC, San Diego Tribune