Electric power steering system, means a low or weak battery or loss of power from the alternator can be enough to cause the steering to stop working. It’s such a common problem on fiats since they first introduced electric power steering on the mk2 Punto in 1999, there are hundreds of threads discussing the problems on this forum
As a one off it might just be that, a one off. It likely still recorded a fault code which would tell you what happened if you wanted to pay someone to plug into diagnostics.