During a backpacking holiday , camping by a lake near Porthleven, it was only as big as a star, but 5 of us say the same, this 'star' moving very fast across the sky, perfectly and quickly zigzagging, and then back again, at a level parallel... weird weird...
This probably was a star. But one orbiting another star, or even a black hole if you saw it do it rapidly, not unheard of. Due to the solstice of other stars (so the way they tilt during rotations, and the tilt looks like a rocking from far away as other stars rotate around it but follow it's tilt) being much different to our summer and winter solstice, you can find that a star appears to shoot from side to side when actually it's simply rotating evenly, but due to their pattern of rotation AND our own, it gives the impression as though the star is moving from side to side.
Not sure which great old timer it was (after reading up on so many I mix them up) but the person who discovered this happened did so by pointing out that the sun doesn't revolve around us, be we and all our planet revolve around it. And he worked this out by mapping ALL the stars, and he found that the sun was the only one in comparison to the rest of the planets that actually stayed still. And all the other planets rocked from side to side whilst swooping around the sun during mapping it.
What was later figured out was the distance the planet rocked from side to side as it swooped gave a distance of how far the planet was away from their star, and how big the star was, and where in relation to their own solar systems they are from each other. From this then they can work out other things like how fast each of the planets orbits a star compared to the rest of the planets.
We then judge whole solar systems doing a similar thing, and we've predicted how far whole solar systems are away from us, and this then gave us a sort of guide as to how far the "edge of the universe" is away. And also at what rate we're expanding.
This then gave us the sad truth that explains why we will never ever reach the edge of the universe, meaning we can never ever explore it all, as by the time we reach to the bit we knew as the edge, the edge would be millions of years further away, and millions of years in our time could be much much longer further away from us.
Or that's how I read the many documentary's, books and websites lol - I've never actually asked anybody.
That all said (and that was a lot I know lol) I hope you're right, and if not and I got all that correct, then what you witnesses was something very unique.
If it wasn't all of the above, it could have just been a meteor caught up in gravity from a bunch of either planet, solar systems, or stars, depending on how far away it was (assuming it was much bigger if it was further away - else you couldn't have seen it through our atmosphere). Whatever it was. Nice one for spotting it.