Ok, almost 3 weeks after having contacted Jolla care and still without news about my Fedex tracking number, I decided to send another mail to Jolla care. 15 minutes later, they replied me with a valid Fedex tracking number. Yes! Things happen!
According to this tracking number, Fedex had picked up my order on December 12 and it "almost" arrived to my address on December 17. Since then it's been waiting in the local Fedex facility in south of France. Now I have good hope my Jolla will be there soon :-)