find my iphone killed my macbook pro

Help. I was just checking out find my iPhone on mt new 5S and was delighted to see my Macbook Pro appear in the list of devices. I decided to lock it to see what happened. After sending the command my Macbook appeared to shut down and then restart with the folder with a question mark in it flashing.

Have I killed my Mac? I know the code but the computer isn't asking me for it. The only thing I can think is I now have an SSD drive in it. I wondered if that might be the problem.

Any help gratefully received!😮