Most likely you got some water in the fuel or your coils decided to go at that time. Running 87 will not harm your car unless there are other things wrong with it.
I have run 87 mostly in my car for almost 100K miles, and I do not baby my car, but it is a daily commuter. On hot days I will get some ping under hard acceleration, but otherwise the car runs fine. Don't jump on it if it pings, or get the higher octane gas.
I have used 91 and 89 and mixed octanes to see how they react in my car. 89 seems to be the best level of mileage and no ping. 87 is a bit more economical(but is it worth it?, I buy out of habit) but will ping on hot days under hard acceleration, so usually I buy higher octane in the summer. 91+ is what the factory recommends so if you want mental comfort or peak performance, use it.
Gas will not cause a misfire unless it is contaminated or you find some cheap really low quality gas south of the border.
Winter gas may have alcohol in it like the guys said. The alcohol will cause any water in the fuel to mix better, but that is not necessarilly good since then the water goes to the engine.
I bet your COPs decided to fail and were flakey for some time before this. they can be flakey for a long time before setting a CEL code. My dealer took a week trying to find my failed COP even after a code was set. Good thing it was under warranty.
Putting new 91 octane in the tank will not be the direct cure for your problem. Clean water free gas is what will do it, UNLESS your COPS are failing, then gas doesn't matter.
If a fresh tank of gas does the job, then avoid the previous station since they may have water or low quality gas. Every dealer can get a load of bad gas or water int the tanks. Let them pump it out before getting another bad load.
If the fresh gas doesn't do it, then you have joined the COPs died club.
Just my opinions and experience,
Jim Henderson
