Question: who switched the sword of gryffindor?
Answer: Why did Snape give the Gryffindor's Sword to Bellatrix to keep? In Deathly Hallows, we find out that, after Ginny Weasley tried to steal the Sword, Severus Snape gave the sword (or rather, a copy, as we find out), to Bellatrix Lestrange to store in Gringott's vault.