+1 to Tim's suggestions, but ...
if you are going to 'rebuild' Moodle on the same server, won't you run into the same issue with the web server issue ('lost access to my server via http')?
Depending upon what 'apparently serious mistake' means, it might be less work fixing access to the web server. Granted, these forums are about Moodle, but a web server is required to run a Moodle.
Since you've mentioned ssh access, that's a clue that server is Linux but you've not disclosed what flavor of linux and if it's on a shared host or dedicated (have root access?).
Not being able to access a web server could have many causes, but some suggestions:
the web server service (daemon) isn't running
- via ssh as root user: ps aux |grep httpd or |grep apache2 (difference there is flavor of linux)
change to configuration created an error and web server cannot launch
depending upon linux flavor, apache error logs should give a clue. Log *might be*
- in /var/log/httpd/error_log and a 'tail -n 50 /var/log/httpd/error_log' command will render the last 50 lines of the web server error log and thus give a clue.
change to firewall (port 80) no longer open.
curl -I http://yoursite/ will check.
'spirit of sharing', Ken