The identity of the so-called Piano Man found wandering in a soaking wet suit in Kent may never be known.
The unidentified man appeared in Kent in April
Since he was found on Sheppey in April, the psychiatric patient who communicates only through his piano music has not spoken a word.
West Kent NHS Trust said on Monday it had checked through most of its leads.
A spokesman said health workers still hoped they could make progress, but it was possible that no-one would come forward with information about him.
The man was first taken to Medway Maritime Hospital where he drew a picture of a grand piano and was then taken to the hospital chapel.
Health and social workers said they were "stunned" when he proceeded to give them a virtuoso performance.
Theories put forward and later discounted included that the man - now in a secure mental health unit in Dartford - was a French street musician and a Czech concert pianist.
The mystery man produced a pencil drawing of a piano
Appeals led to a worldwide response which at its height generated more than 800 leads.
A Norwegian speaker was brought in to try to communicate with the man, in his 20s or early 30s, after he pointed to Oslo on a map.
A ship from Norway was thought to have been in the area when he was found and there were suggestions that his suit was soaked because he had been in the sea.
His social worker Michael Camp claimed that his client "came to life" at the piano.
All the labels had been removed from his clothes when he was found on The Broadway in Minster, Sheerness.
West Kent NHS Trust said on Monday it was possible no one might ever come forward with information about his identity. "We have worked through most leads but we still have some to pursue," it said.