Nodes publishing themselves automatically

This morning, an editor with publishing privileges logged in to review and publish a node that was created by one of our writers, only to discover that it had already been published. Here's the moderation log for the node:

Why was the node automatically published 22 minutes after it was created? This hasn't been a regularly-occurring issue, though I believe it did happen once before.

The only thing I could think of was the Rule that I have set up that re-publishes nodes when they're edited *if* they were already in a Published state, but that doesn't seem to apply to this situation:

Any idea what could be happening?