Wasted spend is reporting zero this month and I do not believe it

Our wasted spend total came back as zero for the current window. Last month it was a few hundred pounds and nothing about how we work has changed. I would like to believe we fixed everything and I have been doing this long enough to be suspicious of a clean sheet. Before I raise it as a fault, is there an innocent explanation I should rule out first? I am wondering whether a change to our campaign statuses during the restructure two weeks ago could be excluding things from the analysis.