Bot deleting rather than reverting

[Former user]

A user replaced free images with copyvio ones on about 20 Australian politics articles. This bot deleted all the copyvio ones, but didn't restore the previous free images, leaving these high-traffic articles without images or with big gaps for almost a week. I had to go and manually restore them, which wasn't an exciting task. This seems quite sloppy and could easily happen again, I hope it can be fixed.