This question already has an answer here:
Currently reading The Hobbit to my daughter, and we came to the Barrels out of Bond chapter where the Dwarves are captured and imprisoned by the Wood Elves. Bilbo sneaks in with his magic ring of invisibility and eventually sets them all free.
But here's what piqued my curiosity: in the chapter it makes clear that Bilbo wore the one ring constantly for a very extended period of time: it specifically states he was down there at least two weeks and then - it's much less clear - possibly for even longer while he came up with and implemented his plan to rescue the Dwarves.
However in The Lord of the Rings, Frodo is constantly terrified of putting on the ring lest he (and the ring) should be located by Sauron. So why does Bilbo, wearing the ring for several weeks, escape detection?
The obvious thought is that Sauron was simply not powerful enough at this time. But that seems a pretty thin claim in many ways. Sauron was powerful enough to be "recognised" as a dangerous sorcerer in his guise as the Necromancer, and to start to gather his followers together. You'd have thought that simply locating the Ring would require a pitiful amount of comparative effort.
Furthermore I believe it's implied in The Lord of the Rings that it becomes increasingly dangerous to use the Ring the closer it gets to its maker (I don't have a reference for this - might be my imagination). If so, things become even more inexplicable since Thranduil's palace wasn't actually all that far from Dol Guldur, where Sauron was holed up.
Any explanation? Or do we have to chalk it up to the poetic license due to a world in development?