US tourist Kelly Jones was probably distressed and disorientated on the day she went missing in south west Donegal, the Belfast Telegraph has learned.
Having now searched the house where she was found alive on Wednesday, gardai believe she entered the premises alone and had been there for at least two days.
Ms Jones (41), a catering services manager who works in South Carolina, went missing on Saturday.
Gardai now also believe she became distressed that day.
She had been in the Glencolmcille area for 10 days on a hillwalking holiday.
Ms Jones' father Ricky is due to arrive in Ireland this morning from his home in Georgia in the US, and make his way to Sligo General Hospital where she is being treated.
Yesterday a garda cordon around the old rectory where the tourist was found was removed. The gardens had been searched twice by volunteers before her rescue.
A pane of glass at the rear of the extensive holiday home was broken, sometime between Monday evening and Wednesday lunchtime.
Asked about Ms Jones movements during her disappearance, Gda Supt Mick Finan said: "The only person who can tell us where she was is Kelly herself. We haven't spoken to her yet.
"We are going to be guided by her medical team in Sligo as to when we can speak to her."
The search, he said, had been concentrated on the mountains around the area because the last confirmed sighting had been there.
"The grounds around the rectory had been searched but we hadn't searched the house. We hadn't expected someone to be actually in a house.
"This house is a holiday home and it was locked up. Kelly was found lying on a couch in the house," he added.
It is thought Ms Jones, who had been due to return to the hostel where she was staying on Saturday morning to check out, was in a distressed state when she was last seen around 5pm that day.
A cousin of Ms Jones has praised the work of the hundreds of volunteers and gardai.
In a message to them, Dana Bailey said: "Thanks so much for not giving up the search for my cousin Kelly. Our family greatly appreciates everyone's efforts."