This happened to my wife and myself. It is extremely serious as it locked her in the car with my children on a busy road. Luckily she managed to figure out a solution by using the mechanical key inside the electronic key and climb out the boot using the mechanical switch.
When it happened to me, none of the electronics would respond, and luckily I had the window open. When I stopped the car and tried to get out the alarm sounded and again was locked inside. I leaned out the window and popped the catch off the handle to access the mechanical door switch.
This is extremely concerning as if this happened during an accident, people could very likely die from being locked inside.
I had both keys in the car and neither responded to inputs, handles would not work either (even with a double pull).