Many of you will be familiar with the Jetpack plugin. I use Jetpack’s Stats module — previously the WordPress.com Stats plugin — to record and display this site’s page views.
Several Jetpack modules including the Stats module require a connection to an account at WordPress.com where your self-hosted WordPress site is given a unique ID. This unique ID is associated with the site’s domain name. If you change an already connected site’s domain name and reconnect it to your WordPress.com account it is given a new unique ID.
Herein lies the source of a problem I had recently which resulted in the apparent loss of all this site’s stats.