Seems MobileJoomla isn't installed now.
How did you setup subdomain? This is a quote from unpublished MJ User Guide:
Mobile Joomla doesn't creates subdomains (that is it doesn't change DNS or webserver settings), but it allows you to use existing subdomains for mobile site version.
The first step to make mobile subdomain is to setup subdomain as an alias to main domain. We usually recommend to disable Mobile Joomla by unpublishing Mobile Joomla Plugin and then get your site working via both main domain and subdomain (that is subdomain displays identical page). Usually webhosters allow either to make aliases directly (there is special field in main domain settings), or indirectly via possibility to set DocumentRoot directory for subdomain identical to the main domain DocumentRoot (note that in most cases it's done at creating of subdomain and you cannot change it further).
After that you can enable Mobile Joomla and test this subdomain for mobile version.