Hi wintry,
Maybe try setting up your HTML/CSS as the template page in a custom theme? You would need to add a bit of extra information to it and create mostly empty theme functions.php and style.css files, but it shouldn’t be much work.
See http://www.wpexplorer.com/create-wordpress-theme-html-1/ for some of the basic required elements.
Hi mj,
Did you do anything right before the posts disappeared, for example switching themes?
Do you have access to the WordPress database? If you do, in the table wp_posts are there any rows?
Is the site backed up? Depending on who your site is hosted with, your host might have an automated back up of the site from 1-2 days ago if the posts were deleted.
Are tags the standard WordPress tags, or are they also a new taxomony that’s been registered?