I ended up downloading LTSpice and running it in that. That way I can see what is happening.
I also changed the top resistor to 750R and called it R1
Bottom resistor to 1K and called it R2.
The capacitor was changed to a floating (not connected to ground) 10V voltage source and called V3.
The switch is closed. Current flows from the initial 10V voltage source, through R2, out the switch to ground.
Zero current flows through R2.
Open the switch. Current now flows though the V3 voltage source, via R1 and R2.
The voltage increases in reference to ground across V3 by 4.28V so the negative side is +4.28 and the positive side is +14.28.
Why 4.28V. Because of the voltage divider formula 750/(750+1000)*10 = 4.28V
But it does not resemble a voltage divider circuit.
Actually, you need to think about things as suggested--think of the floating 10V source as a battery. You can stick a number of batteries in series to add their voltages, each one has its own negative terminal but that terminal is not necessarily system ground. It is ground from what the battery can tell, but it isn't the actual system ground. From that point, think of this as two separate systems--one when the switch is closed, the other when the switch is open. With the switch closed, you can figure out that R1 has 10V at each end (relative to system ground) and as such zero current flow. R2 will have 10V across it and run 1mA. Now open the switch and review the schematic again.
To start, remove V1 and look at what you have with V3 and the two resistors; it's a voltage divider. You've got those equations down, and figured out that with V3 across the two resistors where the midpoint is because of Ohm's law and Kirchoff's laws. Now, add V1 back in (you can do this because of superposition). Try and find a current path from the top of V1 looping back through to its bottom (assume your switch is truly open, not 1Meg as shown). There is no path for current to take.
Also two resistors in series add up the resistance, so a 10V source, 1750 ohms resistance means 0.0057A flowing, and the law that says current flowing in, equals current flowing out. So is there is 10V source at one side of R2, and 0.0057A flowing, Ohms law says 4.28V.
But I am still trying to wrap my head around it.
Voltage source V1 forces the midpoint of the two resistors to be at 10V. No current flows from V1 into R1 or R2, (since current in equals current out), so those currents remain constant at what you calculated for the voltage divider circuit, and the voltage drops on them remain constant. Because you have 4.28V across R1, that forces the top of R1 to be at 4.28V above the positive side of V1 (which is 10V), giving you the 14.28V. Because V3 forces the bottom of R2 to be 10V below the top of R1, it sits at 4.28V.