I've been playing the game for several hours, completed the first dungeon, and reached level seven.

As silly as this may sound, I've just now noticed that party members lose their inventory if they're killed in combat. While I'm not worried about the loot I've previously lost, I seem to have lost at least two quest items.

Is there a way to retrieve these lost quest items without cheating?

Bummer. It's too late to get them I guess.

I'm debating myself between cheating to spawn the lost items or keeping the quests unfinished until my next play-through.

Thanks mate.

It looks like you're not too far into the game. You shouldn't worry too much about that stuff. If you're planning to play again (and you should), finish those quests then.