We had two light switches that were in two separate rooms but controlled the kitchen overhead lights. About two years ago, I disconnected one of the switches. Last night, the switch that was left operational, stopped working for no apparent reason. I tested it and it no longer has power. The breaker did not go off either. I am stumped. Can anyone shed light on why this switch suddenly has no power?

What did you use to check if the switch had power? I am sure youdid this but I am going to ask it anyway... Did you check the bulb to see if it was any good?
The system you have forr switching one light from to different switches is called "A Three way system" normally the power travels through both switches to make the light work, if it just when you flip a switch you only re-route the path the current takes to turn the light on of off which ever the case might be. By using only one switch it is possible that the current is still flowing through the box where the other switch is disconnected.
Turn off the electricity and take the wires off the switch that just stopped working and tie the two wires together together and then turn the power back on and see if you have power to the light. I am assuming that you have three wires going to that switch (not including the ground wire) so if you do have three then there are three different ways to tie two wires together... wire 1 to wire 2... wire 1 to wire 3... wire 2 to wire three.
Try all three combinations until you find two that will give you power to the light, if none of them do then you probably have a problen is the wiring system somewhere.