When Tom and Gilderoy were at school together, the fag system was still in place. It would later be abolished, under Dumbledore's more enlightened lead, but Dumbledore was not yet headmaster then.
Gilderoy, several years younger than Tom, drew what initially seemed like the short straw. He never told anyone about the things Tom made him do. Who is to say if fear or loyalty drove him to keep his silence? But he never forgot them, either.
And after Tom disappeared, Gilderoy embarked on his great career. But behind every book, every signing tour, every public appearance, was the hope that one day Tom would come back for him.
Nobody ever told Legolas that the Istari could die. Belonging as he does to an immortal race, and being young among his people, he has never before encountered death.
He understood from the outset that most of his companions were mortal. He knew all along that the Quest was a dangerous one, and might be deadly. But he had thought that if any were to die, it would be one of the Men, or a hobbit perhaps, or Gimli. Never Mithrandir.
He does not understand how this could happen. He has never felt grief before. But he is still an elf, and he was raised to be stoic. So as he stands in his confusion on the rocks outside Moria, he does not cry.