I accidentally connected ground to the +5V pin and vice-versa on a (W65C22), I don't know how to be sure that I didn't burn the chip.
It's very, very likely that you damaged the IC. Whether it is totally dead, or just partially damaged, would need further checking (unless it's already obvious - you haven't mentioned the results of subsequent checks - what checks did you do so far?). However you can't trust that IC completely, even if it seems to work now.
Symptoms of obvious internal damage include "bubbles" in the top or bottom of the IC epoxy package (due to the die inside the package getting very hot) - even part of the package now being missing - or, as commented, any smell from the IC.
Another symptom of internal damage is an increased current drain (with correct polarity power applied, obviously) sometimes leading to the IC package being significantly hotter than usual.
maybe the chip has some sort of security around power pins so current flows in only one direction, do chips have this kind of protection?
No, typical ICs don't have that type of protection.
when the cables were swapped, when I connected power not even an LED connected from 5V to ground through a resistor would turn on
That behaviour is because your IC drew so much current that the power supply voltage dropped (temporarily), and that is why the LED could not light - insufficient voltage across it, due to the high current through the reversed IC.