Can't recall which site right now, but I know it was a blogspot.com blog. It has also happened in the past with this UserEcho site.

Version 0.4.62 just made a new phantom tab. A site I just opened and then closed, showed up in a different window, but one nested as such.

Group A (saved window)

Subgroup A.1 (saved window)

Subgroup A.2 (saved window)

Phantom window appeared here. Still shows "loading" spinning circle. Claims to be loaded (light blue), but clicking on it does nothing. Has a green dot in the box (saved), but its peers within this subgroup do not. Was able to close it with red trash icon.

Subgroup A.3 (saved window)

Original location of closed window

I keep finding more... 

I looked again, and next to the "las - Google Search" in my memory detail, I now see "about - Google Search". I know that just a few minutes ago I opened a new tab, typed "about" in the URL, erased it (backspace), typed some other things, then closed the tab. I was trying to remember how to get the memory detail for chrome://memory, and having previously been a Firefox user I started typing "about" out of habit (for about:memory). 

As I mentioned before, there's some other "litter" in memory that didn't come from typing in the URL bar, but rather from clicking on a link.

One more hopefully useful bit of info: I closed the tab for this forum post, and it stayed in my chrome:memory list! I did not type the address directly in the URL bar. I clicked on it from my Gmail account after receiving a notification.

It's likely that every tab I've seen with this issue was in a saved window or group. I tend to name a lot of my windows / groups. That might help you hunt down the problem.

As for the strange memory details screen, do you know if that's related? For example, I have the following using 256K right now:

Tab

Google

The one I saw today was in an open, active, and saved (named window).

Sorry - you did ask me that! I'm running 0.4.56

Just saw one where it was marked unloaded after I had closed it, but did not respond to left-clicks.... it was a simple google search. It did not switch windows.

The URLs have varied... random sites seemingly. I no longer can remember what they were. I am 99% certain the tabs changed windows on at least one occasion as well. I will post again if I see it again. It may be a few days before it recurs.

To clarify, I'm not sure exactly when the tabs reappeared in a different part of the tree and different window. I suspect it may have been immediately upon closing, but I don't really know.