I checked ..
Heated front screens. In the screen, if you look closely (easier to see looking from the outside with a pice of paper against the inside of the screen) you will see very thin wavy lines. These are you heater elements. On the Focus there are two models of heated screen, and it is not uncommon for them to stop working. Main culprit, 99.9% of the time is one of the "filaments" (the wavy lines) has broken, thus breaking the circuit. As said, there are two different screens for the Focus; one has the connections at the bottom two corners, and one has the connections at the top and bottom of the screen. On the former, if one of the filaments has broken, usually that will result in that side not working (for example, the passenger side) On the latter design, the circuit is all round, and has "groups" throughout the screen, so small sections can fail, but the rest will continue working.