The road wasn't closed, per se. It was only closed to through traffic. Therefore the restrictions still apply.
Further, unless there were loading restrictions in force (indicated by kerb markings), you could have made your delivery (and avoided a ticket) by parking on the road for the time necessary to make the delivery. Parking on a footway (in an urban area) is always a parking contravention, irrespective of whether there are yellow lines or whether you're making a delivery.
Chris