Brian Laundrie's dad Chris joined the FBI-led search for his missing son and didn't find anything

• Brian Laundrie's father joined an FBI-led search for his missing son in Florida on Thursday.
• "There were no discoveries, but the effort was helpful to all," an attorney for the family said.
• Brian - the sole person of interest in the Gabby Petito case - has been missing since mid-September.

Brian Laundrie's father joined FBI-led search for his missing son - the sole person of interest in the Gabby Petito case - at a vast Florida nature preserve on Thursday, but did not make any discoveries, an attorney for the family said.

Chris Laundrie left his North Port, Florida, home in a pickup truck in the morning hours and then initally entered the Myakkahatchee Creek Environmental Park, which connects to the 25,000-acre Carlton Reserve in Sarasota County where authorities have been looking for Brian Laundrie since mid-September.

He spent several hours at the reserve before returning home.

Laundrie family attorney Steven Bertolino told Insider that the father had been asked to "point out any favorite trails or spots that Brian may have used in the preserve."

"Today Chris Laundrie accompanied members of law enforcement into the reserve to show them the trails and places Chris and Brian have hiked and which Brian was known to frequent," Bertolino said.

Bertolino added, "There were no discoveries, but the effort was helpful to all."

Water has now receded in the sprawling reserve "and certain areas are more accessible to search," he said.

"The entire Laundrie family is grateful for the hard work of the dedicated members of law enforcement that have been searching the preserve for Brian over the last few weeks. Hopefully Brian will be located soon," the lawyer said.

Bertolino explained that though Chris and his wife Roberta Laundrie provided information to law enforcement verbally "three weeks ago" about their sons favorite spots in the swampy area, it was thought "that on-site assistance may be better."

"The preserve has been closed to the public and the Laundrie's as well, but the parents have been cooperating since the search began," Bertolino said.

The lawyer previously told Insider that Chris Laundrie was "asked to assist law enforcement" in their search of the Carlton Reserve on Wednesday, but his involvement in the effort was "postponed."

"Since the preserve has been closed to the public Chris has not been able to look for Brian in the only place Chris and Roberta believe Brian may be," Bertolino said at the time.

The parents reported their 23-year-old son missing to police in Florida on September 17, telling investigators that Brian Laundrie went out for a hike in the Carlton Reserve days earlier with only a backpack and never returned home.

Meanwhile, authorities scouring the snake-and-alligator-infested reserve have discovered the remnants of a campsite in the area that appeared to have been used recently, a source close to the Laundrie family told CNN.

There have been reports that Brian Laundrie is somewhat of a survivalist, including one in which Petito's best friend claimed he stayed in the Appalachian mountains by himself "for months."

"To my knowledge, he's a backpacker," Bertolino told Insider on Thursday.

Petito's mother reported her missing to police in New York on September 11 after her family abruptly lost communication with the 22-year-old woman in late August while she was on a "van life" cross-country road trip with fiancé Brian Laundrie.

Authorities have said that Brian Laundrie returned home to Florida on September 1 with the van the couple had been traveling in and without Petito. He retained a lawyer and refused to speak with authorities.

Petito's body was discovered on September 19 in a remote campsite of a Wyoming national forest and her death was later ruled a homicide.