Don't worry - it's very unlikely it's lost/unrecoverable. :-)
1. Backup the entire DokuWiki directory offsite. This is easiest if you have root access to the webserver. If it's a Debian package it will be installed into several directories. Make sure to tar up the backup to avoid changing permissions and timestamps.
2. Provide more information. The more information you can give us about the setup (OS? Version? Environment - e.g. hosted, shared, etc, Access - e.g. ssh, ftp, webdav, cPanel, etc) the better we can advise you.
3. When you have backed up the installation - check the version of PHP running on the server, run
phpinfo to get the details of the configuration; update all the modules for DokuWiki; check the server logs (and post any errors in your reply, along with the details of your setup). Delete
phpinfo.php after you have run it. Copy the backup tar, do not use the original backup, only work with a copy or copies.
There are several things you will want to recover, of varying importance:-
1. Most important - the wiki data. It will most likely remain intact.
$DokuWiki/data.
2. Important - the wiki configuration, which includes user permissions. It will most likely, mostly, remain intact.
$DokuWiki/conf.
3. Useful - the modules. Some may have changed.
$DokuWiki/lib/plugins. Later examination of textfiles beneath
$DokuWiki/data/pages will allow you to determine most of the modules formerly in use so that you can update the system to cope with modules that do not work with the current version of DokuWiki. Don't update them until you've backed up the old ones (in case the previous administrator modified them).
4. Useful - the template. Probably changed/overwritten. Look at
$DokuWiki/conf/dokuwiki.php to see which template is being used. The line you are interested in is
$conf['template']. The filetime will tell you whether that config file and the template have changed. If you are lucky the previous administrator will have made a backup.
5. Damn handy - the
.htaccess file in the root of
$DokuWiki (it won't have changed).
phpinfo.php - put this in the root of the DokuWiki directory and load it with your browser. Ensure it is owned by the webserver (see my previous comment about giving more detail about the system). Copy the output.
<?php
phpinfo();
?>
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