wp_get_attachment_url() filter

I have been trying to develop a plugin that will allow the user to download the high res images uploaded via eazyest gallery. I started another thread here http://ww.wp.xz.cn/support/topic/cant-get-attachment-page-link?replies=2

I have got to the point where I can do most of what I need, provided I am on the attachment page (in a child theme). For a attachment page of a given post ID say 201 If I call wp_get_attachment_url(201) I’ll get the correct URL, e.g. the URL to the high res image like http://127.0.0.1/hiresimages/windsurfing/Baja-2013-8142.jpg.

Though if I call the exact same function from my plugin e.g. wp_get_attachment_url(201), I get one of the WP media manager URLs like http://127.0.0.1/luckybeanz/wp-content/uploads/windsurfing/Baja-2013-8142.jpg

I assume this is due to some filter eazyest gallery implements, though I can’t tell which filter it is. Does anyone know and can you comment here on how to invoke it? It may be contained in http://eazyest-gallery.googlecode.com/svn-history/r228/trunk/themes/twentyten/loop-eazyest-image.php

https://ww.wp.xz.cn/plugins/eazyest-gallery/