setquk's father was sat in a car parked at the side of the road, presumably in the driver's seat, with the window open, and was using a mobile phone.
Someone came along on a motorbike, reached in through the open window, and grabbed his phone with the intention of stealing it.
He was quick enough to get hold of the would-be thief's arm and wind the window up, with the intention of trapping the thief there and summoning the police to arrest them.
Unfortunately, the thief escaped (but suffered some broken fingers in the process, presumably as setquk's father tried to hold him there); and unfortunately, although setquk's father was able to give the police the licence-plate number of the motorcycle the thief was using, this didn't help to track it down because the motorcycle was also stolen (and I guess the thief abandoned it shortly after this incident).
setquk sees this as another example of the same phenomenon described in the article and by dtf: opportunistic mobile-phone thieves on motorcycles.
