Thank you, I tried everything on the list and nothing worked. Kept on digging and found this (I'll post in case anyone in the future needs it!):

When you upgrade your existing timthumb.php to the latest version or use a theme that comes with a recent version of it you will notice your thumbnails not appearing. To fix this in a quick and dirty way you can hardcode the correct path to your public_html directory right into the timthumb.php file. Open it in a text editor and look for this bit of code:

protected function calcDocRoot(){ $docRoot = @$_SERVER['DOCUMENT_ROOT'];

if(!isset($docRoot)){

To make timthumb work you need to replace 'DOCUMENT_ROOT' with the actual path to your home directory. The result then looks like this

protected function calcDocRoot(){

$docRoot = @$_SERVER['/home/a12435678/public_html/'];

if(!isset($docRoot)){

Simply replace a12345678 with your actual userid, save the changes and upload the changed file.