Hi Trish,
I can confirm that there was a JY representative at the airport. The reps are booked to start 4 hours prior to long haul flight departures, this assistance is purely at check-in (not airside) and on occasions if you arrive and check in before the rep attends you would not see a rep at all.
Specifically to this flight, there were a few major issues that would have taken up the reps time and there is a possibility that in dealing with them he would have been away from his post, helping customers at the BA ticketing desk.
I am sorry that you missed him, but I hope you understand that there may not always be a rep around at all times.
Kindest Regards,
Monty