Asking the obvious, but there was nothing that came out with the oil when you emptied the sump?
I have seen flattened flakes like this, and they came from a (crankshaft) bearing that had momentarily run dry. This is not great, but not always fatal. The flakes are generated by the steel surface of the crank contacting the actual aluminium of the bearing. They are momentarily caught in the bearing and flattened and broken up by the pressure of the power strokes coming down on them. This is why they are all the same thickness.
If you have an insurance case running for the accident, you should probably get a mechanic to write a report for you.
With overhead cam engines, when a sump pickup runs dry it tends to be the top of the engine that suffers first. I repaired an engine once that had run out of oil, but "saved itself" by pinching the cam, which then skipped a few teeth on the cam belt and stopped the engine from compressing and firing. This would not happen on a chain driven cam system, but the flakes could have come from the cam bearings as well. There were no flakes in the car I worked on as rotation stopped stopped instantaneously.
You likely should inspect the cams (relatively easy) and sump (a bit more involved) before driving. Or you can take a risk, buy a decent amount of oil and filters do a lot of oil changes while crossing your fingers.. it doesn't matter a huge amount if you buy a lesser quality oil if you are changing it every couple of days. Put decent stuff in when you are not seeing any more flakes and specs.
It is a ****ty bit of advice to give, but be slightly more prepared for something failing in this engine. If you feel any unusual vibrations, it could be a damaged bearing failing. It will shed more flakes if that happens though.