Did you even read about that case? That person deliberately collected the seeds which had the round-up ready gene in them. The courts at all three levels noted that the case of accidental contamination beyond the farmer's control was not under consideration but rather that Mr. Schmeiser's action of having identified, isolated and saved the Roundup-resistant seed placed the case in a different category.
The evidence showed that the level of Roundup Ready canola in Mr. Schmeiser's 1998 fields was 95-98%
I did read it, yes. I find that the notion that farmers can no longer choose to keep seed for the next crop -- like they used to for millennia-- to be ridiculous. They can't do that now, because it's now wrong to. Because if they do, the seed has genes they're not allowed to have without a license.
To me it sounds like the issue is with capitalism, not GMOs :-P From a scientific perspective though, you don't want to save the seeds anyway. They are created from two plant strains and as such benefit from hybrid vigor, which means they'll produce more seeds than later generations will. This isn't GMO specific, non-engineered crops also use this same technique.