Bluetooth corruption on 2013 Macbook Pro
I found some workaround that will at least spare you a reboot when problem arrives. It may be found here: https://discussions.apple.com/message/23705326#23705326

Shortly, type in terminal:

sudo kextunload -b com.apple.iokit.BroadcomBluetoothHostControllerUSBTransport
sudo kextload -b com.apple.iokit.BroadcomBluetoothHostControllerUSBTransport


After doing this your devices should reconnect. I have the same OS Version (10.9) and Early 2013 Macbook Pro and it works with my problems with bluetooth keyboard.