Well it's obviously normal if you w'ont see an agent there, probably not assigned that time or heck could be at another security zone,whichever is more busy..ahh well everytime i been there..there has always been an agent, i think they only there during rush hours..between 6-9am and 4-8pm
My advice is if you're running late, like within minutes of departure and not boarding ...proceed to a security agent and ask them if the airline agent is around