As he was only 31 at your last 'sighting' of him, there is plenty of scope for him to have moved anywhere and done anything.
Have you ruled out this death -
Jan/Feb/Mar 1964
Chatham
William H Bridger aged 82.
Was he married in 1911? Childen? Is he described as 'deceased' on any of children's marriage certs? Have you found his wife's death (if she had a more unusual Christian name than he did it might be easier to pinpoint) and seen if he was the informant on her death cert? When did father, Frederick die? Did he leave a WIll - if so did it menton William, maybe with an address too if he was executor?
Just some ideas to narrow down when and where he may have died.