Redirect with querystring htaccess

[eluser]JanDoToDo[/eluser]
Hey guys.

I am completing payments on my site, and when a request is processed it returns the user back to :

/account/complete?oid=15

I'm not using querystrings and so it cannot find the page. How can i redirect this so the the oid is a slug in the uri? I have this:

RewriteCond %{QUERY_STRING} .
RewriteRule ^(.*)$ /index.php/%1? [L]

But it doesn't work - The page now displays, but I want the querystring as a uri segment, or otherwise just someway to get it.

Any ideas?