The location for the admin folder (re-named or not) is built from the admin/includes/configure.php file.

I'm sure that you will have edited this to reflect your new folder name, but for some reason the changes haven't gotten to randomcharacters321/includes/configure.php.

There are a few possible reasons for this. The two that I usually do are loading the revised file back to includes/configure.php where it is ignored; and uploading the file to the right place, but having the upload silently ignored by my server as the original is sitting there write-protected. To solve the latter I usually completely delete the version on my server so that there is no obstacle to the new version being uploaded.

HTH.