We sometimes experience products selling out suddenly in the middle of a large campaign. There is now a “Get Shortlink” button next to your permalink when you edit or write a post, and when you click it you’ll get a popup with the beautiful link already highlighted for your copy and pasting pleasure.
Use Custom Short URLs in my books and newsletters to encourage trust and build brand loyalty with fans. Some will show up as a referral from a webmail address, like mail.yahoo.com.
See if you are using Classic Analytics (ga.js) or Universal Analytics (analytics.js).