For one thing, Frodo was not by himself
when attacked by the Nazgul on Weathertop. On pages 262-263 of Chapter 11, A
Knife in the Dark, in The Fellowship of the Ring it says that
after they see the Nazgūl at the top of the dell:
"Terror overcame Pippin and Merry, and they threw
themselves flat on the ground. Sam shrank to Frodo's side. Frodo was hardly less
terrified than his companions; he was quaking as if bitter cold, but his terror was
swallowed up in a sudden temptation to put on the Ring. He felt Sam looking at him, as if
he knew that his master was in some great trouble, but he could not turn towards
him. He shut his eyes and struggled for a while; but resistence became unbearable,
and at last he slowly drew out the chain, and slipped the Ring on the forefinger of his
left hand. Immediately, though everything else remained as before, dim and dark, the
shapes became terribly clear."
You all know the rest, Frodo gets stabbed in the shoulder
by the Morgul knife, and barely manages to pull the Ring off of his finger and see Strider
jump out of the shadows with flaming brands of wood just before he passes out. This shows
however, directly from the words of almighty Tolkien himself, that the other three hobbits
and Strider were with Frodo at the time of the assault. My explanation for
Weathertop remains flawless, and hopefully true!