[Haldir]

well, you already said all my thoughts but I
got one more "may-be-theory":
Smeagol was a hobbit from the Anduin,
Bilbo was a hobbit from the Shire, Hobbiton,
Smeagol didn't know where's the Shire so I
can guess he never been there.
Gandalf said that the Shire is the only place
he saw hobbits, and if there were hobbits in
the Anduin at the years 3430-3440~ of the
seconed age, Isildur would discover them, and
if they were there later, some other king of
Gondor would discover them.
Unless there weren't real hobbits, Gondor knew
those halflings, there were even some poems
about those halflings.
Smeagol was some kind of halfling, but he was
no hobbit, because the ONLY real hobbits were
living in the Shire.
That's why the people of Gondor were never at
the Shire but still knew the halflings.
That's why Sneagol never saw hobbits, but he
wasn't scared of them, because they've must
reminded him his former friends... halflings !