I guess that's the reality for most adults that go missing.
People have mentioned the similarities with the Nicola Bulley case; the speculation, etc.
Some people have also said that he would surely have been found now as it's 'such a small island'
Don't forget that the initial suspicion that Nicola had gone into the river turned out to be the right one. She was there all the time, right under everyone's noses.
The police and authorities in any country are not infallible. I used to work in the police force here in the UK. We would send dozens of officers out to comb an area on hands and knees where we thought a person had gone missing. It often took weeks, because we were looking less than half a mile adrift of where they were 'last spotted' or expected to have been. One of the most recent disappearances was eventually found in a shallow pond that had already been searched by police divers, two weeks afterwards.