Happened to me just yesterday on Cademimu. I was using my sorc healer. Anytime loot dropped that wasn't something I could use, I would just "pass". Everything came up with Cunning which was perfect for the smuggler in the group. The other two, a Sentinel and a Guardian didn't get anything either. Last drop is a lightsaber with Willpower main stat. The guardian needs it.
I'm done. No more PUGs for me. I'm ok with not getting drops in lowbie FPs like that. I'm not ok with people needing on gear they can't use or intend on using for a companion. Also keep in mind, the Knight's companion does have WP as a main stat but cannot use a single blade lightsaber to be effective.
Did you actually ask the person about that? I needed on a strength lightsaber once on my sage (I didn't read carefully enough), saw the mara need on it too and immediately went, oh crap, that wasn't for me was it? I won the roll and started a trade with him right away. No fuss, no muss.
Sadly, if I hadn't said anything, I don't think he would have either - I think he would have gone away angry about the 'ninja' even though I may just not have realized it. And had I not seen him need on it, I wouldn't have realized it until later when I went to equip it (so him just saying 'hey, that was for my class' would have fixed the whole thing).