With Jetpack, your stats information is connected to a unique blog ID. Sometimes, if a site owner was using a development site or a different address when they set up Jetpack, disconnecting may create a new blog ID. When this happens, it may appear that your stats were lost.
That's what happened on your site; it previously used a different site URL, pottblog.eu.
I have fixed the issue, and you should be able to get your Stats and Subscribers back by going to the Jetpack menu in your dashboard, and disconnecting / reconnecting to WordPress.com.