ReallySimpleCaptcha.php code remaining after deleting plugin years ago

Had a few major site issues this past week, mainly so I’m told to do with php usage etc… however, when our engineers went through the logs to see what was causing the issue, it appears that there is still some references to ReallySimpleCaptcha.php appearing in the logs – we deleted this plugin years ago when we moved to iThemes Security Pro which has a Google ReCaptcha v3 element.

An excerpt from the engineers ticket:

“The error message does refer to open_basedir restriction, however the filename ReallySimpleCaptcha.php it is trying to find is not present at all on the entire server, so loosening directory access restrictions would not make a difference.

The log message is of the form:

[Thu Jan 18 20:24:35 2024] [proxy_fcgi:error] [pid xxxxxxx :tid xxxxxxxxxxxx] [client xxxxxxxxxxx] AH01071: Got error ‘PHP message: PHP Warning: ?file_exists(): open_basedir restriction in effect. File(ReallySimpleCaptcha.php) is not within the allowed path(s): (/var/www/vhosts/websitedomain/:/tmp/) in /var/www/vhosts/websitedomain/httpdocs/wp-content/plugins/minimal-coming-soon-maintenance-mode/framework/public/include/misc/geoip/autoload.php on line 39’

This does seem to have been warning (not showing critical failure) for some time regarding ReallySimpleCaptcha.php, well before the issue was reported.”

(coding numbers, IPs and actual domain removed from excerpt for security)

Any ideas as to (a) why it is still somewhere in the system, and (b) how do we remove it safely to prevent it being logged all the time and / or causing the issues.

Thanks in advance.
TONY