Computer - I lost my tablet now I have no idea where it is it is swiched off the last time I saw it?

If the device is not powered on, there are no features that will help you in that regard. I'm sorry :( However I suggest you retrace your' steps from the last time you remember having it, and if/when you do find it, install the "Where's My Droid" App, it bypasses any and all settings provided that the device has power, and rings uncontrollably when it receives an activation phrase buy email or text.