The Swedish diplomat who secured the release of 29-year-old Australian, Alek Sigley, from North Korean detention said the moment he was told Sigley could leave with him was one of “great relief and great joy”.

Sigley was freed from detention in North Korea on Thursday after going missing for more than a week, and on Friday released a statement pleading for privacy and saying he wants to return to “normal life”.

He thanked Sweden’s special envoy to North Korea, Kent Rolf Magnus Harstedt, who was asked by the Australian government to raise Sigley’s case with the North Korean government on its behalf, due to Australia not having an embassy in North Korea.

Harstedt didn’t even have confirmation Sigley had been arrested when he met with North Korean officials, the diplomat told Radio National on Friday evening.

“We didn’t have any valid info about his wellbeing or what situation he was in,” he said.

“One thing I can say is when I brought up this matter, the North Korean side was open to this kind of dialogue with me.”

Harstedt has conducted similar operations seeking the release of prisoners before, but said this was “not standard”, and he expected it to take much longer than it did.

“I must say the moment when they told me ‘you are going to get him out with you’, it’s a moment I will always remember,” he said.

Harstedt said he had “an idea” about why Sigley was detained, but would leave that up to the Australian to tell his own story.

Sigley has reunited with his wife Yuka Morinaga in Tokyo following his departure on Thursday, he said in the statement, adding that he would not be holding a news conference or doing any media interviews.

“I just want everyone to know I am OK, and to thank them for their concern for my wellbeing and their support for my family over the past week,” he said. “I’m very happy to be back with my wife, Yuka, and to have spoken with my family in Perth [Australia] to reassure them I’m well.”

“I intend now to return to normal life but wanted to first publicly thank everyone who worked to ensure I was safe and well.”

Sigley also thanked the Australian prime minister, Scott Morrison, and foreign affairs minister, Marise Payne, for their efforts, as well as those in the government who worked to secure his freedom.

“There are many other people whose names I don’t know who worked hard in the background as well. I’d like to thank those at the Department of Foreign Affairs in particular,” he said.

“My family and friends are always a source of love and support but have been even more so at this time. I also appreciate all the good wishes that myself, my family and my friends have received.”

Sigley had been studying a master’s degree in Korean literature at Kim Il Sung university, and ran a tour company that organises trips for foreign students.

He was believed to be the only Australian living in North Korea.

It remains unclear why Sigley was held in detention.