商品購入ページでその商品が購入されたフラグを実装する

{% assign already_order = false %}
{% for customer_order in customer.orders %}
  {% if customer_order.cancelled == false %}
    {% for orderd_item in customer_order.line_items %}
      {% if orderd_item.product_id == product.id %}
        {% assign already_order = true %}
      {% endif %}
    {% endfor %}
  {% endif %}
{% endfor %}