Have you finished the game? If so, I found it that those missions come out often. I didn't get my swords in a while like you but I was so addicted to my clan that I couldn't start a new saving- so I was running around until one day... the mission came up!

And Westen Paladin and Skyblade- You are both right and wrong... some are repeat-able... but some are unfortunatley not. You've got to be careful, I suppose.

A common mistake in chucking out good mission items is to press 'A' constanly to cut the blabbering, then it comes to the item swapping (when your inventory if full of mission items [DAMN ADAMANTITE TAKING UP SPACE! well, atleast for me!], it gives you the option to swap around items)- people keep pressing 'A'. They don't realise- until they saved and it's too late... oops!

OR

You have too much of something (Adamantite for my sis) so you clean things out... 'Discard Adamantite? Yes/No?' 'Yes', 'Discard Adamantite? Yes/No?' 'Yes', 'Discard Adamantite? Yes/No?' 'Yes', 'Discard Black thread? Yes/No?' 'Yes'.
Saving... saved. Oh crap.