Unrequested "Your Apple ID Verification Code is:" texts
I occasionally get text messages on my phone that say "Your Apple ID Verification Code is: 1234" (for example). They are from "504-72", which I believe is Apple.
Why is Apple sending me verification codes when I'm not asking for them? I thought that it only sends a verification code if I'm trying to reset my password, and only after I successfully enter my recovery key. Could this mean that someone somehow got a copy of my recovery key?
Is there any way that someone else's attempts to unlock his iCloud account are being sent to my phone?