You mean stole? Where do you see this in the link you provided?
That's what I read in the article.
> As established in the original Federal Court trial decision, Percy Schmeiser, a canola breeder and grower in Bruno, Saskatchewan, first discovered Roundup-resistant canola in his crops in 1997.[4] He had used Roundup herbicide to clear weeds around power poles and in ditches adjacent to a public road running beside one of his fields, and noticed that some of the canola which had been sprayed had survived. Schmeiser then performed a test by applying Roundup to an additional 3 acres (12,000 m2) to 4 acres (16,000 m2) of the same field. He found that 60% of the canola plants survived. At harvest time, Schmeiser instructed a farmhand to harvest the test field. That seed was stored separately from the rest of the harvest, and used the next year to seed approximately 1,000 acres (4 km²) of canola.
Used their technology, yes, barely. Stole it? Well, the courts unequivocally didn't feel like he damaged (deprived?) Monsanto of anything.
You are thinking of https://en.wikipedia.org/wiki/Monsanto_Canada_Inc_v_Schmeise.... He is often harelded by anti-GMO activists as an example of the dangers of GMOs and Monsanto, but the fact of the matter is that the "cross contamination" is a myth. He deliberately took cultivars from his neighbour's plot and analysis showed that they comprised a significant portion of his crops, which wouldn't be possible by cross-pollination alone.
Should seeds be patented? Are Bayer, Monsanto, Syngenta, and agrochemicals companies evil? These are all worth discussing (the answer to the second question is yes), but that particular myth is not.