They say to donate organs (or volunteer to do so upon your death) and some people are too simple for 3-syllable words, so they pronounce Oregon as organ. So when they heard the clerk say organ, they thought they were hearing Oregon. So they're donating Oregon.
But it's the most distinguishable state shape and easily the most famous US state. Don't they at least teach about William S. McLoughlin in world history? Everyone knows "that story" about when he worked as an aide to Portland Mayor Baker in 1913