Arias was last seen in Longview, Washington on November 26, 2001. She and her mother, Guadalupe Castro, were planning to go shopping with Castro's estranged husband and Arias's father, Gregario Arias Ibal, in Portland, Oregon during the day. They were going to buy clothes for Castro's unborn baby. Ibal was located but neither Arias nor Castro has been heard from again. Castro had been estranged from him but was thinking of reconciling with him at the time of her and Arias's disappearances. Arias and Castro had lived together with Castro's parents for about a year prior to November 2001.

The vehicle they had been riding in, Ibal's Jeep Cherokee, was discovered abandoned in California sometime after their disappearances, parked at the residence of one of his relatives. He dropped it off there, and left a message on his relative's answering machine. There was no sign of Arias or her mother at the scene. Their disappearances are considered suspicious. They left behind all their clothes when they disappeared.

An anonymous phone caller to Castro's family said that Castro was in Arizona and ill, but the person did not provide any specific details. The call was placed from Tucson, Arizona. Authorities do not know if the information provided is accurate. Castro's parents believe Ibal was involved in their daughter and granddaughter's disappearances, but no evidence has been uncovered to substantiate this theory.

Arias and Castro's cases remain unsolved.