When sheriff’s deputies arrived at Green Lake in Wisconsin in August to search for a man who had failed to return from a solo fishing trip the day before, they found his vehicle and trailer parked beside a boat launch and a capsized kayak in the lake, suggesting that he had drowned.

But after 54 days of searching for his body, investigators said on Friday that they had found evidence that pointed to a different fate. The man, Ryan Borgwardt, they said, faked his death and left the country as part of an elaborate, monthslong plan.

Mr. Borgwardt, 45, a husband and father of three from Watertown, Wis., was reported missing on Aug. 12 after he went fishing in his kayak on Green Lake, about 65 miles southwest of Green Bay, said Mark A. Podoll, the Green Lake County sheriff.

Sheriff Podoll said that Mr. Borgwardt’s vehicle and trailer were found near Dodge County Memorial Park, where people launch their boats. The kayak was later found capsized in a part of the lake that is over 200 feet deep, he said.

The next day, the sheriff said, he brought in Bruce’s Legacy, a nonprofit that specializes in recovering drowning victims, to help search for Mr. Borgwardt’s body using sonar technology. Two fishermen casting nets recovered a fishing rod that Mr. Borgwardt’s wife confirmed belonged to her husband, Sheriff Podoll said. A tackle box was also found later that day with his keys, wallet and driver’s license inside.

At the end of August, investigators began using cadaver dogs and divers to search for Mr. Borgwardt’s body, Sheriff Podoll said. Bruce’s Legacy searched about 1,500 acres of the lake, the Green Lake County Sheriff’s Office said in a news release.