{% comment %}
  By default, we'll assume we haven't found the index.
{% endcomment %}
{% assign page_index = 'Unknown' %}

{%- for possible_post in site.posts -%}
  {%- if possible_post.title == post.title -%}
    {%- assign page_index = forloop.rindex -%}
    {%- break -%}
  {%- endif -%}
{%- endfor -%}


{% comment %}
  If we found an index, zero pad it, if necessary.

  Thank you to https://stackoverflow.com/a/37453646 for this solution!
{% endcomment %}
{%- if page_index != 'Unknown' -%}
  {%- assign page_index = page_index | prepend: '00' | slice: -2, 2 -%}
{%- endif -%}

Issue {{ page_index }} - {{ post.date | date: "%B %-d, %Y" }}