Snapchat has always had the option to provide my mobile phone number in the iOS app so people can find me by my number. I've never filled it in because I was always uncomfortable giving out my phone number to some random app. When the data breach happened, I checked and my phone number was not in the leak.

To clarify: the only way your phone number would be known by Snapchat and thus could have been leaked is if you provided it to Snapchat manually, correct?