If there is only one and that looks good no reason to suspect it isn't doing it's job not allowing too rich or too lean conditions from fouling it or burning it up.
I have to ask if you reved it up and kept it constant there at the rpm you said it was missing and check for the misfire then? Although you could guess by looking at the plugs or use both to confirm both.
Before finding the problem, first you have to recreate it first so you can test. If not the problem may be hidden. If it's truly intermittent even at a specific rpm, then it may be wiring, so wiggle tests may help to recreate it.
Since of so many fuel injectors a faulty injector would also cause a miss on 1 or more cylinders and could be intermittent due to wiring because they are electric driven by grounds through the ecm/pcm.
I heard of anytime you have an engine performance problem, hook up everything you got, but an oscilloscope but a cylinder balance test was all that was good for. Hook up a tach, timing light, fuel pressure gauge, vacuum gauge, code reader or since OBDI that key chain jumper, go around and inspect the exhaust and take it for a ride or not. Keep an eye on everything looking for a fault while reving up and down, wiggling wires, spraying starting fluid around checking for leaks, covering the air horn making it stall, making it run rich.
By now with the misfiring the plug or plugs taht have been misfiring are probably fouled by now but maybe not if still intermittent. Nonetheless, they should be inspected to look for rich or lean mixtures, oil or carbon, etc and might as well replace them.
If you ever find the misfire, swap a spark plug wire and check again. If still misses there and didn't move than either disconnect the fuel injector wires and do a balance test like that to see if it makes a change. If after that and nothing measure camshaft lobe lift on both valves.