Use page.find with list fields?

Is it possible to use page.find in a list output because having no joy?

This outputs as expected {{ page.find('/mypage').header.tagline }}

but I can't get it to work here...

<ul>
{% for list_page in page.header.list_page %}
{% set page = list_page.folder %} ---> where folder is the url /mypage
{% set ptag = page.find('page').header.tagline %}
<li>
<a href="{{ page }}">
{{ ptag }}
</a>
</li>
{% endfor %}
</ul>

Tried
{% set ptag = page.find('page').header.tagline %}
{% set ptag = page.find('{{ page }}').header.tagline %}