Plot hole: Phoebe's ex-boyfriend Clay shouldn't have known Prue worked at the auction house. Phoebe says she hadn't talked to him since she left New York, and when she arrived in San Francisco, Prue was still working at the history museum.
Plot hole: After Piper and Leo lose their sins, Piper mentions that Lukas has Prue. But there's no way she could have known that, since she was unconscious when Prue was taken.