I come across this problem as every so often my Macbook Air is closed and Bluetooth is off. I have easy access to my keyboard but can't get my bluetooth trackpad to work as it is disconnected. This webpage gave me a quick reminder on how to get around this.
Option 1:
Command + Spacebar (to turn on Spotlight) - type Bluetooth File Exchange, and Enter.
Option 2:
Command + Spacebar (to turn on Spotlight) - type Bluetooth, Select the Bluetooth pref pane icon (it is blue), Control + F7 to toggle the Tab button for selections, and Tab through until you land on Turn Bluetooth On.
Happy typing. I actually recommend disconnecting your mouse or trackpad for a day to learn the many keyboard shortcuts that exist (just going online and Back in college my mouse broke and I had no choice but to learn these for a week until I got a new mouse. I have never regretted having these skills.
