Though the vigil was organized by Susan Powell's family, her father Chuck Cox said he had no idea Joshua Powell would be there.
"We have no contact of Josh at all," Cox said Sunday. "I didn't know he was coming up here."
Susan Powell, 28, has been missing since Dec. 6 after Joshua Powell, 34, last saw her in the couple's home before he took their sons on a late-night camping trip into a freezing winter storm. Since he faces no charges, police cannot stop him from traveling out of state.
Joshua Powell stood with his son, 4-year-old Charlie, in a chilly downpour Sunday night with dozens of others at the candle-lit vigil and spoke briefly with Susan's sister, The Associated Press reported.
A Utah court issued a subpoena to three Salt Lake TV stations to obtain original video tapes of interviews with Powell following his wife's disappearance.
"Lots of times I just go camping with my boys," Powell told a local CBS News' affiliate then. "Just overnight. We do s'mores and stuff."
Joshua Powell agreed to a police interview early in the investigation, but he became more uncooperative as the search wore on, police said. He failed to show up for a scheduled interview with investigators Dec. 14, and the following day answered only a handful of detectives' questions, West Valley City Police Capt. Tom McLachlan said. Powell was later named a person of interest by police.
The couple was reportedly seeing a marriage counselor and facing daunting financial problems. The Salt Lake Tribune reported the two had filed for bankruptcy, and public records revealed they were $200,000 in debt, including large amounts of credit card debt and student loans.
Joshua Powell's father, Steven Powell, said his son has been "vilified" by speculation.
"The whole thing has just turned into a vilification of Josh, and it will turn into a vilification of me, my ex-wife and my other kids," Steven Powell told The Salt Lake Tribune Sunday.
Steven Powell said Joshua told him he had been fired from his job as a computer programmer for a trucking and warehousing company.
Susan Powell's Father-in-Law Wavers
Cox initially defended Joshua Powell but has since wavered.
"I don't know until we get some solid info about what really happened that night, that morning, that day," Cox said Sunday. "Still a lot of unanswered questions."
Last week, Cox indicated to "Good Morning America" that he began doubting Joshua's story.
"I asked him if he had any idea where his wife, my daughter Susan, would be. And he said he didn't. He was sincere sounding when he said that. I believed that," Cox told "GMA."
When asked if he still believed his son-in-law, Cox replied, "I don't know what to think anymore."
Cox said that he has no choice but to leave the investigation up to police.
"I understand the concerns I'm hearing from everyone, and I can see their point," he said. "I just don't want us to focus on him exclusively or that story exclusively when there might be another explanation."
Police told ABC News they have been back to the Simpson Springs Campground where Powell told investigators he had taken his young sons on a camping trip in the early morning hours of Dec. 6, but they could not find any evidence that verified his story.
ABC News has learned that fewer than 20 people visit the remote campground each winter. The temperature the night Powell allegedly took the couple's sons, ages 4 and 2, to the campground was between 10 and 25 degrees, with rain and snow. Powell told police they set out for the trip around 12:30 a.m.
Investigators have been at the Powell home and forensic tests were run in portions of the house, but were not expected back for weeks.
Anyone with information regarding the case can call West Valley City Police at (801) 840-4000.