I have no idea what version.php is but it's surely possible to convert an external file into a plugin -- I've done it several times. Can you post your plugin?
version.php was a file I created that had all of my version checking, for my products here on vbulletin.org, being done from that file.
The contents of my plugin are in the first post
I'll post it again though.
Hook location: misc_start
Plugin code:
PHP Code:
if ($_REQUEST['do'] == 'my_product_id') { echo '<version productid="my_product_id">1.2.3</version>'; }
(which SHOULD allow me to call the version by going to mysiteurl.com/misc.php?do=my_product_id)