I've had players against me resign merely because they've lost their queen. Is this etiquette?
Merely resign because they've lost their Queen? Even in bullet chess nobody should say "merely lost their Queen".
Anyway, I believe you are talking about blitz, seeing as how that's all you play here so no I don't believe there is any serious etiquette.
Personally, I do expect people to resign before the point of playing purely for a stalemate in any format, but opinions vary and I wouldn't worry about it.
Well, losing a queen is a sure loss most of the time, even losing a piece. At your level, in blitz the advantage can shift easily, so etiquette is something you should not worry about right now.