[Plugin: Simple Fields] Showing image by field title

I am able to show an image from a custom field using the code example at Tips and Tricks:

<?php
$image_id = get_post_meta(get_the_ID(), "_simple_fields_fieldGroupID_1_fieldID_1_numInSet_0", true);
$img_src = wp_get_attachment_url($image_id, 'thumbnail');
?>
<img src="<?php echo $img_src ?>" alt="An image" />

However, when attempting to show the image using the title of the field rather than the ID, it doesn’t display. Is it possible to do something like:

<?php
$image_id = get_post_meta(get_the_ID(), "IMAGE-FIELD-TITLE", true);
$img_src = wp_get_attachment_url($image_id, 'thumbnail');
?>
<img src="<?php echo $img_src ?>" alt="An image" />

?

This would be incredibly helpful as I am working across three servers (production, staging, and development), and this would allow me to avoid having to change the IDs for all custom image fields with each migration.

http://wordpress.org/extend/plugins/simple-fields/