Rails: It shows nil in the database, can this solve the main issue?

If a seller sells something, I'm unable to show the user who bought it.

class UsersController < ApplicationController
    before_action :authenticate_user!

  def show
    @user = User.find_by_name(params[:id])
    @product = current_user.products.where(availability: true)
    @purchased = Sale.where(buyer_email: current_user.email)
    @sales = Sale.where(seller_email: current_user.email)
  end

 private

    def post_params
        params.require(:user).permit(:name, :email)
    end
end

sales.html.erb:

<% @sales.each do |sale| %>
    <tr>
    <td><%= link_to sale.product.title, pickup_path(sale.guid) %></td>
    <td><%= time_ago_in_words(sale.created_at) %> ago</td>
    <td><%= sale.seller_email %></td>
    <td><%= sale.amount %></td>

If I go ahead and change it to <%= sale.buyer_email %>, it just shows me the current user and what THEY just bought rather than WHO bought their item. This is what I get after checking the console, the seller_email is nil and the amount is nil for the last sale. How do I fix this so that the seller can see who go their item?

>> Sale.last

    Sale id: 2, buyer_email: "dave64@gmail.com", seller_email: nil,
    amount: nil, guid: "71363abb-8921-3d5c-a4d4-200fa2855ae",
    product_id: 2, created_at: "2015-05-24 06:07:23", updated_at: "2015-05-24 06:07:23"

This is the transactions controller

  class TransactionsController < ApplicationController
  def create
    product  = Product.find_by!(slug: params[:slug])
    token = params[:stripeToken]

    begin
      charge = Stripe::Charge.create(
        amount: product.price,
        currency: "usd",
        card: token,
        description: current_user.email)

      @sale = product.sales.create!(buyer_email: current_user.email)
      redirect_to pickup_url(guid: @sale.guid)
    rescue Stripe::CardError => e

      @error = e
      redirect_to product_path(product), notice: @error
    end
  end

  def pickup
    @sale = Sale.find_by!(guid: params[:guid])
    @product = @sale.product
  end
end

The is the products controller

class ProductsController < ApplicationController
  respond_to :js, :html

  def index
    @products = Product.where(availability: true)
    respond_with(@products)
  end

  def show
  end

  def new
    @product = Product.new
  end

  def edit
    authorize! :manage, @product
  end

  def create
    @product = current_user.products.new(product_params)
    @product.save
    respond_with(@product)
  end

  def update
    authorize! :manage, @product
    respond_to do |format|
      if @product.update(product_params)
        format.html { redirect_to @product, notice: 'Product was successfully updated.' }
        format.json { render :show, status: :ok, location: @product }
      else
        format.html { render :edit }
        format.json { render json: @product.errors, status: :unprocessable_entity }
      end
    end
  end

  def destroy
    authorize! :manage, @product
    @product.destroy
    respond_to do |format|
      format.html { redirect_to products_url, notice: 'Product was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

  private

  def product_params
    params.require(:product).permit(:title, :image)
  end
end