Gandalf....fortune teller??

[Galadriel55]

Originally Posted by Zigûr

Is it not possible that, given that he was wearing his own Ring, Gandalf could tell when someone put on the One? I believe Galadriel also knew that Frodo had worn the Ring without asking him.

I think I always assumed that Gandalf somehow could just "tell", "magically" if you will, that Frodo had worn it, or had guessed.

I think that may well be true, but the issue of the thread was that Frodo only put the ring on months after Gandalf wrote the letter. Even had Gandalf witnessed it himself in person, he still shouldn't have mentioned it in a letter he wrote way before.