The family of a woman who died in a California hospital in 2023 said in a lawsuit that they had not been informed that she had died, leading the family members to believe she had been alive and missing for nearly a year.

Jessie Peterson, 31, had been admitted to Mercy San Juan Medical Center in Carmichael, Calif., a suburb of Sacramento, for treatment in April 2023, but her family was not notified when she died, according to a lawsuit filed this month in the Sacramento County Superior Court by her mother and sisters. Instead, the lawsuit said, Ms. Peterson’s mother had been told that her daughter had been discharged against medical advice.

It took another year for Ms. Peterson’s family to learn that she had died.

“We’re still very sad, and we still don’t have any answers,” Ms. Peterson’s mother, Ginger Congi, said in a video interview. “It’s hard to not be angry.”

The last time Ms. Congi spoke to her daughter was on April 8, 2023, when Ms. Peterson called her and asked to be picked up from the hospital. She had been admitted two days earlier, on April 6, 2023, for a diabetic episode. Ms. Peterson was pronounced dead less than two hours after she called her mother, according to the lawsuit, and her body was transferred to a cold storage facility the next day.

Ms. Congi, who was listed as Ms. Peterson’s next of kin, called the hospital on April 11, 2023, and asked to be transferred to her daughter’s room, but was told there was no one there with her name, according to the lawsuit. Her mother asked more questions and was told that her daughter had left against medical advice.

Mercy San Juan Medical Center is operated by Dignity Health and owned by CommonSpirit Health. Dignity Health declined to comment on the lawsuit but said it extended its “deepest sympathies to the family during this difficult time.”