This may not be too good news for T-Mobile Sidekick owners out there as apparently T-Mobile Sidekick user’s data may well be lost for good reports an article over on pcmag.

Last Monday Danger Sidekick handsets lost data services and lost access to calendars, address books and other services which Microsoft stores in the cloud, then on Saturday T-Mobile along with Danger made an announcement to Sidekick customers stating that the data “that is no longer on your Sidekick almost certainly has been lost as a result of a server failure at Microsoft/Danger.”

Danger and T-Mobile strongly advise Sidekick user’s not to completely discharge their Sidekick battery or even remove it as this would eliminate the address book and other stored data.