He thanked Ms. Petito for “putting up with me through Utah, a topographic playground.”
Mr. Schmidt said the last time that he and Ms. Schmidt heard from Ms. Petito was around Aug. 23, when she said she and Mr. Laundrie were leaving Utah and driving to Grand Teton National Park in Wyoming. The last post on her Instagram account is dated two days later.
“From everything we saw in the photos and the videos and when we spoke to her, they were having the time of their lives,” said Mr. Schmidt, who went to Wyoming on Tuesday night to make contact with the authorities who were searching for Ms. Petito. The park said in a statement that rangers were working with investigators from the National Park Service, the F.B.I. and other local authorities to find Ms. Petito.
Her father, Joseph Petito, who had moved to Florida to be closer to his daughter, is staying in touch with the authorities there, Mr. Schmidt said.
“It’s a parent’s worst nightmare,” he said.
Ms. Petito, the oldest of six siblings, had been working as a pharmacy technician to save money for the trip. She met Mr. Laundrie at Bayport-Blue Point High School on Long Island, Mr. Schmidt said. They began dating after graduation and moved two years ago to Florida, he said.
In some of her posts in 2020, Ms. Petito appeared excited for a future as a couple.
On March 17, Ms. Petito and Mr. Laundrie took a selfie against the backdrop of the California coast. “One whole years worth of adventures and stories down,” she wrote, adding: “a lifetime to go.”
On July 2, she posted a throwback photograph of their first date, their heads together, wielding chopsticks. “Here’s a picture from our first date because I have so much love for you. Brian asked me to marry him and I said yes!”
Using his Instagram handle, she wrote: “@bizarre_design_ you make life feel unreal, and everyday is such a dream with you.”
Michael Levenson and Christine Hauser contributed reporting.