Compared to the relaxed atmosphere down in the cave where the locket was retrieved so easily, things were far less straightforward for Dumbledore.
Not to mention how difficult it was to find the Horcrux hidden inside the Room of Requirement. With the directions provided by Wenxiu Lord, it still took Dumbledore and a disguised Gellert Grindelwald quite some time to track it down.
The Resurrection Stone ring inside the Gaunt Shack was a different story entirely.
Chapter 477