Your stars will return
Yesterday the Club Nintendo service in Europe was having some issues. In addition to downtime, some users are reporting that their stars (coins in the US version) are not appearing in their account.
Nintendo has noted that although the downtime problem is solved, you may not see all of your stars back yet. If they are erased, don’t panic! The publisher will apparently return them to your account soon. Some users are reporting to us that everything is all good, but a few are still having trouble, so just give it some time before logging in again.
Nintendo of Europe [Twitter]