[This](https://scifi.stackexchange.com/a/60061/28222) (and others eg: [this](https://scifi.stackexchange.com/a/49704/28222) ) answer states that Frodo claiming the ring alerted Sauron immediately of its position, which makes sense: How else would Sauron realize where the Ring and Frodo were at that exact moment. And it also explains why Sauron did not know where the ring was beforehand.

However there is a problem with this: Why did Sauron not find out about where the ring was when it was in Gollum's possession? Gollum obviously claimed the ring as his own (he even dreamt about becoming Gollum the Great, unfortunately I'm not able to find the passage in the books). In addition Bilbo claims it as well (right before he leaves it for Frodo), without alerting Sauron (Sauron learns about the Shire from Gollum, not through some form of comunication with the ring) 

Is there an in canon explanation, or have I simply misunderstood something?