Luke Scott said about 2 years ago on Importing and Exporting CSV Data :
I added the account_number field fairly recently.

Showing in the schema:
  create_table "customers", force: :cascade do |t|
    t.string "name"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.string "account_number"
    t.string "sla_number"
    t.string "mobile_phone"
    t.string "work_phone"
    t.string "home_phone"
    t.string "municipality"
    t.string "main_product"
    t.string "contract_name"
    t.date "contract_from"
    t.date "contract_to"
  end

And looks to exist in the table when I browse it.

Stopped and started my rails s for good measure.

It's very strange and had my head spinning for a while trying to diagnose it.