[HairOfTheDog]

He alludes, yes. In Hobbiton, he says that he found Gollum, but that the enemy found him first. In Moria at the "talk" scene, Gandalf and Frodo speak as if Gollum had either escaped or been set loose from Barad-Dur... For good or ill, the story was not complicated by the period he was held captive in Mirkwood, or that Legolas had traveled to Rivendell to report the escape.

[Corin Stormhands]

That's right. I think it would've complicated things for the movie...

[RosieCotton]

He alludes, yes. In Hobbiton, he says that he found Gollum, but that the enemy found him first. In Moria at the "talk" scene, Gandalf and Frodo speak as if Gollum had either escaped or been set loose from Barad-Dur...

This, actually, is kind of a logical flaw in the movie: Gandalf knows what words the enemy got out of Gollum in torture, but how?? He never mentions having spoken to Gollum, and in Moria, Gandalf and Frodo speak as if Gollum had been at Barad-Dur all this time. So how did Gandalf know?