Bernard Ross, 51, left his home in Oxford, UK, on October 18th, telling family he was going to visit his sister in London, but he never arrived.
The former executive was diagnosed as bipolar and hospitalized after leaving his job at the Nyon-based Uefa in December last year.
Last month his wife Jacinta Ross told The Local it was possible her husband had returned to Nyon or around the St Cergue area where the family had lived half the year for 11 years.
After nearly two months without news, Ross is thought to have turned up in Nyon at around 9.40pm last Friday, Thames Valley police said in a statement.
In a press release, his wife said Ross was spotted on CCTV visiting Uefa's offices where he spoke to security guards, telling them he wanted to deliver Christmas cards to five Uefa directors.
Bernard is described as 5ft 7ins tall, of medium build. He is a fluent French speaker and is believed to have been using a bicycle to travel around, though he was likely travelling on foot on Friday.
Chief Superintendent Christian Bunt of Thames Valley police said: “We are continuing our investigation to locate Mr Ross as we have increasing concerns for his welfare. It is believed he does not have access to the medication he requires.
“We are working closely with police in Switzerland and international authorities as part of our continuing efforts to try to locate him.
“I would like to reiterate that if anyone sees Mr Ross, they should call police immediately so that we can check that he is safe and well.”
Anyone with information should call Thames Valley Police on 0044 1865 841148 or Vaud police on 021 644 44 44.