Yes, you can, I believe. I recall seeing once that if you don't pick up the bag of loot that Omega Mark XII leaves behind, you will never, ever be able to get it again, thus preventing you from ever buying a Wyrmhero Blade from the Bazaar. Don't know if there are others, though, but I do believe this one is correct. I think it was the Godslayer's Badge of something? =3