I have been using WordPress Stats plugin for long time. And when Jetpack  was introduced, I had it installed right away. Everything works great. What I like about WordPress statistics data — from this plugin — is that it can give me some useful insight about my blog traffic. It’s not as detailed as Google Analytics, of course. But, it’s useful.
Yesterday, I made some modifications on the blog theme. I was not sure whether this problem has something to do with the issue or not. But, when I logged in to my WordPress dashboard and hit the Stats Page I found an error. Something regarding the invalid token.
I disabled Jetpack plugin, and had it enabled again. I did it using the standard procedure: install, connect to WorPress.com account, and configure.

All works. But, not the statistics. All statistics are gone.

I have some statistic profiles under a single WordPress.com account. I checked the other sites, and they’re all working. I’m still looking for a solution for this. I feel that all the statistics are stored at WordPress’ server. I think I will try to contact them. For now, I think I will use Google Analytics data and server log.