question - was his weapon a gold or purple weapon? Is your weapon white, blue, purple or gold?
You'll find that people will want to only buy "gold" weapons because they have this fixation that gold = best. It doesn't matter if your blue weapon of dooooooom has the exact same stats as someone else's gold butter knife... people will go for the gold weapon. Heck, your weapon could have better stats, be max damage and the other weapon 1 less than max with crummy mods... but if it's a "gold" weapon then people will want to buy that over your "garbage"
If your weapon is gold.. then state it is gold and you'll easily sell it... if it's purple.. you might be able to sell it.... if it's blue or white.. then forget it as no-one will buy it

.. try starting a "WTS" thread here on these forums in the selling forum.. thats likely to be your best bet of selling it if it's not gold...