I'm having trouble believing that one person can accomplish this in 12 days with few tools could disassemble a car and build something even remotely drive-able without a welding torch, engine jack, and countless other tools. Was he stranded in the desert in the way that I imagine?(no water, sand dunes everywhere) Or did he end up in some desert town that had basic facilities for him to do this type of work?
Even the most skilled machinist would have a tough time doing this. Seems implausible.
A Citroen 2CV is pretty much tinfoil with an engine attached. It's definitely feasible even with hand tools.
With respect to survival, if you head into a desert, you take supplies galore. The 12 days was probably due to the heat so you can only work at dusk/dawn and seek shelter during the day to conserve water/rations. 2CV is very simple and can carry a lot of stuff. It's nearly ideal.
I take a 72 hour pack and am happy doing 50mi+ on foot if i go more than 10mi from home after a couple of experiences being stranded in rural areas in the UK. Imagine what that guy was carrying in the desert!
It's stated that he didn't have to go far; one of the reasons he didn't just abandon the car and walk was the amount of tools that he'd be leaving behind to be stolen, so...
Even the most skilled machinist would have a tough time doing this. Seems implausible.