Linda Darleen Thacker, 65, of St. Onge, South Dakota, was last seen by family members on the afternoon of August 18, 2025, around 1:00 p.m. A family member's last contact with her was an unanswered text message sent at 7:31 p.m. that same evening. When she remained out of contact, a family member requested a welfare check from the Lawrence County Sheriff's Office on August 19, 2025. Investigators, working with the Crook County Sheriff's Office in Wyoming, used technology to trace Thacker's vehicle — a silver, four-door sedan — to a remote, rugged area of the Black Hills known as Boundary Gulch, roughly 10 miles south of Beulah, Wyoming, near the South Dakota–Wyoming state line. Personal effects believed to belong to Thacker were later recovered approximately 0.7 miles from the vehicle. Thacker is described as 5 feet 6 inches tall, weighing approximately 150 pounds, with blonde hair and blue eyes. She has tattoos on both hands extending from her pinkies to her wrists. She was last seen wearing faded jean shorts and a light-colored, possibly blue, T-shirt or shirt.
The Lawrence County Sheriff's Office and the Crook County Sheriff's Office led a joint, multi-agency search beginning the evening of August 19, 2025, drawing at times more than 35 personnel per day. Resources included search-and-rescue teams from Spearfish, Crook County, Weston County, and Sheridan County; the South Dakota National Guard/Air National Guard; six K-9 teams trained in scent detection, tracking, and cadaver recovery; helicopters; drones equipped with thermal imaging; and certified human trackers. On August 28, 2025, at 8:00 a.m., Crook County Sheriff Jeff Hodge announced the suspension of active search operations in Boundary Gulch, stating that extensive efforts had produced no additional evidence of Thacker's presence in the area but that "this decision does not mark the end of our efforts — our investigation remains ongoing." Investigators continue to follow leads including cell phone data and family interviews. Authorities have noted, without confirmation, indications that Thacker may not wish to be located; the case remains open, and search operations could resume if credible new information is received. As of this writing (November 2025 reporting, the most recent located), no further public update has been issued. The case is logged with NamUs as MP150140 and with the Lawrence County Sheriff's Office as case #25-335. Anyone with information about Linda Thacker's whereabouts is asked to contact the Crook County Sheriff's Office at 307-283-1225 or the Lawrence County Sheriff's Office at 605-578-2230.
