Ungrounded circuit that works

The opamp has a referenced power source, same with logic gates.

@rich11292000 But if the SPST is opened, the entire circuit fails and it requires a ground, right? Pardon any electro-n00bery on my part.

Correct, but if you build a opamp equivalent circuit with no ideal components you will see the real life results. Results dependent on opamp design. This equivalent circuit will need a ground.

So this exact circuit wouldn't work in real life?

To save space in the simulator, what is not shown is the amplifiers +&- power supply and earth, look at the amplifiers configuration, they ask for the +&- voltage.

The floating source could have undesirable dc bias. To keep the source from floating away, place two 10k resistors to the opamp ground, connect the first resistor to the positive of the floating supply, connect the second resistor to the negative of the floating supply. http://everycircuit.com/circuit/5449312208420864

Ground is not a must for circuit in general. Think about a battery powered circuit which does not have ground. But the simulator does not start before you define a zero volt reference point in your circuit. Voltages are always given between two point and the simulator gives you all voltages referenced to your zero volt reference. And as rich already said, there is a ground reference hidden in your OpAmp 0V. Actually unfortunately there is already a zero volt reference inside which makes it impossible (or very ugly to interpret) to run OpAmps on a different level then this ground symbol 😡. Hope this helps.

Here an example how to run an opamp at a differnet potential http://everycircuit.com/circuit/6116122171801600 unfortunately this is only useful for FIXED voltage levels ...