The Referrer type, including Social Network, depends on the data passed in the document.referrer by the browser. A browser sets this document.referrer only when it had opened the current web page by following a previous web page.
Snapchat is an app. When you click a link in Snapchat, you're opening a link in an app, which your web browser then loads. To the web browser, there was no previous web page before that. So the browser doesn't set anything in its document.referrer, and so AA does not track any Referrer type, and so the Snapchat source is tracked under Typed/Bookmarked.
This is very important to remember: the Referrer type depends on the browser being able to set its document.referrer, which depends on there having been a previous web page. The same behaviour arises when following links from any app to a web page, e.g. links from email, WhatsApp, even Twitter links if they are clicked on in the Twitter app, etc.
In general, you should always add a campaign tracking code to your links that belong to campaigns and that you want to identify in your AA reports explicitly.