There's more to this problem than just a disappearing widget. No matter how many times I add the clock/weather widget back to the screen, it disappears again. When I go to add it back, a number of odd behaviors are observed.
1. The case of the disappearing off into the nonexistent zone.`
This happens when I select a new screen and tap the widget.
You see the widget appear to launch off the widget list to the screen but it doesn't land on the screen, it appears to land outside of the top of the screen and if there was more space on the screen, I'd scroll up and expect to see it. This is very odd and you'd have to see me do it to believe it.
2. The case of "not enough room"
This happens after the phantom add described in step 1. I attempt to add the same widget or a different time widget to the same "apparently" empty screen and I get a not enough room error.
Something is hiding on my screen and taking up space. If I press in the same 'apparently" blank screen, I get a design frame object (it's a green, square outline with a diamond on each edge to grab and expand the frame.
If I let go, the frame is no longer visible. However, I long press the "apparently" blank screen and move my finger to the top of the screen where I can dump this frame into the trash can (even though I can't see the frame).
Developer mode is not enabled.