Your instincts about the article smelling kind of skechy are almost certainly right. Yes, that's what your source says happened, but as you note, they don't back it up with anything. If there's one thing I've learned, it's that anti-GMO activist groups are, if anything, even less trustworthy than international megacorporations when it comes to spinning the truth, omitting important factors, or just making stuff up from whole cloth. They're up there with creationists and anti-vaxers when it comes to needing to follow up on the primary documents for every claim they make.
If an article quotes those activist groups and they phrase something in such a way as to "not exclude" what they want you to think but not to actually come out and say it, it's usually not a real thing. If it was, they'd be pounding the drum and saying it outright and stating the facts clearly. My guess is when you hear meaningless phrases like "Monsanto went after" instead of "Monsanto threatened/filed suit against" what they really mean is that an investigator went to the farmer and asked if they were saving unlicensed GMO seeds, didn't find evidence of a violation, and then closed the case.
From what I've actually been able to verify, actual actions against farmers are extremely rare. Only a handful have actually gone to court, and the cases I've followed up on by reading the court decisions have been obviously one-sided with the farmer obviously intentionally violating the rules. The fact that when they're asked for specific cases, their big figurehead "victim" is usually Percy Schmeiser
(side note: This is Monsanto's web site summarizing the situation and they
link to the relevant decisions, which should tell us something) is an indicator that there isn't much in the way of real collateral damage here.
I'm generally pretty quick to believe accusations against big corporations because they're very often true. Unfortunately, the anti-GMO lobby has done so much to burn my trust that I'd take a peek outside if they told me the sky was blue. Will Saletan at Slate has a good summary that just scratches the surface of the whole mess here