I think what you’re noticing is development on this Wishlist item:
As far as I’m aware, they’ve been tinkering with device offline/online notifications for a while (I’ve seen them on a few Cams), and if you look to enable that feature (navigate in the app to Account ➜ Notifications ➜ Push Notifications) you can see a toggle for Device Connectivity Notifications (Pilot), so I think that’s still a work in progress. I don’t know if there is or will be any sort of user-accessible log or if those “disconnect/connect” occurrences will be treated like “events” at any point, so something like what @StevenA suggests may be an answer, depending upon which version of Android you’re using. (I’m seeing it on one phone with a more current stock Android version but not on another that runs an older version of Android.) I believe there are also third-party apps in Google Play Store that can log push notifications if you have a need to track that sort of thing, manage history, etc., but I don’t have any hands-on experience with those particular features.
I plugged in a spare Cam OG for a while today and then unplugged it after a while to create an “offline” condition but didn’t see a notification, so I haven’t been able to see if that’s showing up in Android’s “Notification history” on the phone where I enabled that. I would expect it to, but, again, this is still listed as a “(Pilot)” program.
Also, thanks, @StevenA! I didn’t realize that was a feature built into at least some Android versions, so I enabled that on one phone today to try it. 