Why did all ceiling fixtures (light and fans) stopped working at the same time, while everything else works? Ceiling fans/lights are in different rooms. The breakers are all on.
If you are sure that the lights are on an isolated circuit, then that pretty much narrows it down to a broken connection in the run of cable between the first light fixture/switch box and the breaker box.
I would first take a closer look at your circuit breaker panel. Often when a breaker flips, the actual handle does not physically flip to the off position.
If your breakers have view windows, be sure to look at them instead of at the latch handle to see if on of the breakers shows red or possibly white. If so, flip this breaker off and back on to reset it.
If the breakers do not have a viewing window but you know which circuit is for the ceiling fixtures, trying flipping its latch handle to off then back on. On the other hand, if you don't know which breaker supplies the ceiling fixtures then look for any handle that may not be fully seated in the on position or whose position does not match the other breakers and try flipping it off and back on.
If after your closer look at the breaker panel, everything seems correct then that leaves you with either a bad circuit breaker or a break in the circuit as described by Ed Beal and N R.
I would try to identify the first non working lamp or switch location, I don't usually see lighting circuits fail from back stabs but it has happened especially if fed from a outlet circuit where back stabs were used. More often on light circuits I find a broken wire or loose wire nut at a pigtail , I believe this is because light switches are pulled more often than outlets ( that is my theory as they have less back stab failures than outlets). It could be a white or black wire causing the failure. Look at the last working device on the circuit or the first non working that will be the location of the failure.