Journalist Lorena Hickock's unfinished autobiography gives some clues as to where a private path up to Highfields may have existed.
Here are some excerpts from Chapter VII: The Lindbergh Kidnaping Story --
"A day or two after my arrival in Hopewell, "Ambling" Ashton and I were cruising around when he stopped the car by a farm at the foot of the hill on the side opposite to that up which climbed the driveway up to the Lindbergh house."
"There's a path up the mountain on this side," he said casually. "Lindbergh, he uses it going in and out when he don't want nobody to see him. You go through this here barnyard --"
"I literally fell out of the car, rolled under a fence, raced across a barnyard, rolled under another fence, and stared up the hill. Barely discernible even in broad daylight there was a path -- steep, narrow, almost covered with underbrush, but a path!"
"I told no one about it until the next time Mark Barron came out..."
"I told him about the path and took him out to see it. It would be our "ace in the hole" if we ever had to get up that mountain in a hurry. We also decided that, if we ever did have to use it, either he or I should go, taking a photographer along."
"It was a bad night outside. There had been a blizzard the day before, a thaw that day, and now the temperature was well below freezing, with the wind howling along the deserted highway like a pack of wolves. But this, I decided must be the time to use the path up the mountain."
"Slowly and cautiously, with his lights off, Ashton approached the farm at the bottom of the hill and parked his car as far off the road as he could get."
"It probably took us twenty-minutes to get up to the top. It seemed like half a day. Finally, after a stretch so steep that we practically had to crawl up on our hands and knees, we came to the edge of a level, spacious clearing and there before us, perhaps fifty yards across the snow, stood the Lindbergh house, dimly outlined in the lights from its windows...."
"After a long last look I turned around and, resisting the impulse to get up and a run, crawled back through the snow, found Eddie, and we started down."
"We somehow managed to get off the path going down and for what seemed like hours we were lost. Eddie finally left his camera and tripod with me and wandered about until he found the path and led me to it. I think the most beautiful landscape I ever saw was that barnyard, with the shadowy outlines of Ashton's car in the background, when we finally stumbled out to it."
Hickock's unfinished biography includes 17 pages on the Lindbergh kidnapping, and is at the Franklin D. Roosevelt Library in Hyde Park, New York.
Also, another reference to the path up to the house:
Beasley, Maurine. "A 'Front Page Girl' Covers the Lindbergh Kidnaping: An Ethical Dilemma." Summer/American Journalism, 1983: pages 63-74.
"Hickock hit on a bold plan. Shortly after her arrival in Hopewell, "Ambling" Ashton had shown her a secret path up a mountainside leading to the Lindbergh estate."
"Taking along an A.P. photographer, Eddie O'Haire, and refusing the plea of a male reporter to go in place of her, Hickok set forth, driving to the bottom of the snow covered path in Ashton's car. "