Odd occurrence 12/2/18

I was on an S7 between Turnham Green and Gunnersbury when it stopped at the signal just beside the Sainsbury’s car park. After a couple of minutes, two staff came out of the cab into the passenger area, then opened one of the doors. They then looked out of the door, closed it and returned to the cab. A few moments later, another staff member left the cab and walked along the track. He was carrying a stick type thing, and proceeded to poke around under the train. At this point, the train lights went off. The staff member was joined by another before, around two minutes later, they walked back towards the cab carrying something which appeared to have come from under the train. The lights then came back on, and we proceeded to Gunnersbury. There was at no point any PA announcement explaining the reason for the delay.

What happened?