What's the meaning of this joke? Johnnie: I didn't know where the Azores were...

Johnnie: I didn’t know where the Azores were.
Pa: Serves you right. Aren’t I always saying you’ll get into trouble one day for not remembering where you’ve put things?
Why Pa says"where you’ve put things"???

Papa doesn’t know that the Azores are an island group; he ignorantly thinks that the Azores are his son’s belongings.