Report it. I reported a broken-into shed, even though nothing was taken. It looked like the burglars were disturbed as they left a spade lying in the middle of the lawn. I dithered all day about reporting it, but eventually did, using 101. Two uniformed officers can round straight away and had a look and checked to see if there was any possibility of taking prints from the spade handle (not, unfortunately). They did say that reporting little things like this is very important as, as Snazy said, they can add up to a bigger picture.