Continuity mistake: When Aunt May is falling off the building, her purse is on her right arm. The next shot shows the purse on her left arm. (00:52:05)
Deliberate mistake: When Spider-Man attempts to rescue Aunt May from Doc Ock, May's umbrella handle latches onto the building's angel sculpture, so the angel is to her right. After Stan Lee's cameo, as May shouts, "Help me!" the watch is on May's right wrist instead of her usual left. When Spider-Man shouts, "I'm coming," next shot of Aunt May shows her hanging from the opposite side of the angel's body. Then Spider-Man shouts, "Hang on," and in the next close-up of Aunt May her watch is on her right wrist again. (00:50:40)
Answer: Unless there is is a deleted scene to shed light on the issue, then it's not really addressed in the movie. It's possible that Doc Ock and Harry had a second meeting that took place off-screen in which Ock revealed to Harry where his hideout was, but as there's nothing really to go on, it's anyone's guess and it's reasonable to consider it a plot hole.
Phaneron ★