As someone said above, accidents happen, but not with masking agents.
It's a diuretic. It's not like you buy them over the counter as masking agents; there are loads of ways to end up taking them without perhaps knowing. I'd be more inclined to see what the real story is before getting all righteous about it. It's entirely possible he was doping but 6-months suggests a technical violation, not that the authority decided he was on a serious dope run.
Even Bassons got a 1-year ban for missing a test from the French authorities (and doping is illegal in France) so I imagine there's more to the six months than just they want to let him off; he's hardly a well known name outside his own particular discipline.