The case of a Bay Area couple in their 70s who disappeared over the weekend from a rental home in Inverness continues to baffle both their family and Marin County authorities.

Married couple Carol Kiparksy and Ian Irwin were last seen and heard from on Friday, and they never checked out of the Airbnb cottage as they were supposed to on Saturday. As the Marin Independent Journal reports, housekeepers who arrived to clean after the couple's checkout time found all their personal belongings still there, including laptops, cellphones, and wallets — and their car was still parked outside. The home is on Via de la Vista, uphill from Chicken Ranch Beach.

The couple's family has yet to comment, but they have visited the cottage and reportedly "agreed [with authorities that] there was nothing out of place."

In the four days since they were reported missing, search and rescue professionals and an all-volunteer, 135-person search team have been combing through nearby woods, Tomales Bay, and the Point Reyes National Seashore — one original theory was that the couple had gone on a hike. As ABC 7 reports, neither sonar-scanning boats nor dogs have come up with anything.

Kiparsky, 77, is a retired linguist who has written several books, and the ex-wife of Stanford linguistics professor Paul Kiparsky. Irwin, 72, is a Parkinson's disease researcher and the former director of neurochemistry at the Mountain View-based Parkinson’s Institute.

Foul play is not suspected in the couple's disappearance, and at this point neither is the possibility that they were injured or stranded on a hike — though the area is dense with vegetation.

Sgt. Brenton Schneider with the Marin County Sheriff's Office tells the Marin Independent Journal, "It’s baffling. We have no leads. No clues. They left out of nowhere." And, as he says to ABC 7, "The [family is] sad, they are worried about Carol and Ian, and they want them to come home safely. So, that's why we are still out there searching."

Speaking to the Mercury News, Michael St. John, a search-and-rescue manager on the operation in Inverness, says, "The disappearance doesn’t make sense or fit with profiles that are common," noting that neither of the two had an sort of dementia. "They are good-functioning people and the area around Inverness is not somewhere we get this happening. But we haven’t stopped looking."