A 73-year-old hiker has been missing for one week after he vanished on a hiking trail in southwestern Colorado, National Park Service rangers said.

Thomas Irwin was last seen hiking the Petroglyph Point Trail in Mesa Verde National Park at about 1:15 p.m. Monday, Jan. 15, rangers said on Facebook.

Then someone turned in a cellphone believed to be his to the park’s museum the next day, rangers said. The Petroglyph Point Trailhead is near the Chapin Mesa Archeological Museum.

The 2.4-mile, strenuous loop trail follows the “foot-worn trail of the Ancestral Pueblo people into the forested Spruce Canyon landscape” and “is narrow, rugged, and rocky, with several steep drop-offs along the canyon wall” leading to a large petroglyph panel about 1.4 miles south of the trailhead. It takes about two hours to hike.

“Dehydration and altitude sickness are common problems at Mesa Verde,” according to the National Park Service.

Hikers should drink water, rest often, and avoid walking along the unstable cliff edges.

The National Park Service is seeking more information from the person who turned in the phone, as well as anyone who visited the park Jan. 15 and might have seen Irwin.

Mesa Verde National Park is located near Cortez, just north of the Ute Mountain Reservation and about 30 miles west of Durango.

Irwin was last seen wearing a dark gray flannel shirt with horizontal white lines, dark gray pants and tan hiking boots, rangers said.

In comments on Facebook, someone said they saw Irwin as he was starting and their hiking group was finishing the trail to the petroglyphs at about 1:30 p.m. that day.

Many speculated whether the missing hiker could have gotten lost on the trail.

“I hope someone checked the trail from the Petroglyph panel to Little Long House! It could be easy for someone to get confused and take that trail thinking it was a continuation of the Petroglyph Point trail,” someone said.

Another person shared they had gotten lost on the trail a few years back.

“Do a lot of people get confused on this trail? We did when we took it several years ago, we were unsure where to start going up, the trail started to become narrow and we finally found the stair-step switchbacks area,” they said. “We were hesitant and felt like we should continue to go south instead of up but once we made it to the top it was obvious we were still on the trail.”

Someone else shared a photo of deep snow covering the trail from the week before.

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