Hearing Only One Megillah Reading
Question
I was able to hear an evening Megillah reading this year. But I missed the morning reading because I had to catch an early morning flight, which was unavoidable. I mentioned this to someone whom in turn told me that the mitzvah is to hear the reading twice, and if you listen to only one reading but not the other, you have not fulfilled any mitzvah at all. He said he learned that from his rabbi. Is that really true?