Sidebar is appearing on custom post pages without being called - php

Question

I'm creating a Wordpress theme for a graphic portfolio website, and I'm utilizing the sidebar.php for a hero image on the index page that is not meant to appear on other pages. While this works for all static inside pages, I have two custom post categories, and the sidebar section has started appearing above those posts.
I should note that this hasn't always been a problem, and started cropping up for no apparent reason while working on something else.
On index.php, the sidebar is called as follows:
<?php get_header(); ?>
<?php get_sidebar(); ?>
<?php
if ( have_posts() ) : while ( have_posts() ) : the_post();
get_template_part( 'content', get_post_format() );
endwhile; ?>
<nav>
<ul class="pager">
<li><?php next_posts_link( 'Previous' ); ?></li>
<li><?php previous_posts_link( 'Next' ); ?></li>
</ul>
</nav>
<?php endif;?>
<?php get_footer(); ?>
While page.php is similar but lacks the php line calling the sidebar, as follows:
<?php get_header(); ?>
<div class="row">
<div class="col-sm-12">
<?php
if ( have_posts() ) : while ( have_posts() ) : the_post();
get_template_part( 'content', get_post_format() );
endwhile; endif;?>
</div> <!-- /.col -->
</div> <!-- /.row -->
<?php get_footer(); ?>
page-fine-art.php also lacks that php line, as follows:
<div class="row">
<div class="col-sm-12">
<?php
$args = array(
'post_type' => 'fine-art',
'orderby' => 'menu_order',
'order' => 'ASC'
);
$custom_query = new WP_Query( $args );
while ($custom_query->have_posts()) : $custom_query->the_post(); ?>
<div class="blog-post">
<h2 class="blog-post-title"><? php the_title(); ?></h2>
<p class="blog-post-meta"><?php the_date(); ?> by <?php the_author(); ?></p>
<?php if ( has_post_thumbnail() ) {
the_post_thumbnail();
} ?>
<?php the_excerpt(); ?>
<?php endwhile; ?>
</div> <!-- /.col -->
</div> <!-- /.row -->
<?php get_footer(); ?>
The function creating the the custom posts for "fine art" goes:
function create_my_custom_posts() {
register_post_type( 'fine-art',
array(
'labels' => array(
'name' => __( 'Fine Art' ),
'singular_name' => __( 'Fine Art' ),
),
'public' => true,
'has_archive' => true,
'supports' => array(
'title',
'editor',
'thumbnail',
'custom-fields'
)
));
I don't see where sidebar.php is being called in the final example, or where else it could be coming from.