H/Flyer - the metal you describe would have shown up in either the oil filter or in oil analysis.
OK, we know that almost nobody does oil analysis because they don't know or because it adds £10 to each 50hr check
but the oil filter should be cut open and it is clear this is not always done either.
Reports from U.S. engine shops suggest that some 95% of shock loaded engines are OK but they only NDT the gears, not change them. However, IMHO, your problem was not the gears (if the engine stopped in soil over several revs) but a bent crankcase which caused a lot of bearing interface material to be shed into the oil. I gather the gears are very rarely found to be damaged.
Oil analysis............. cheap at 10x the price.