I know this is a bit late so I am going to post my answer for people who might encounter the same scenario. There are few things that you can do:
Request a backup of your website from hosting company and then compare live version with that backup (as suggested by @RiddleMeThis)
You can you check
meta_key column of
wp-options table to see if there are any unused
meta_key entries (as suggested by @Jos) but if the website has changed a lot in the past then you may get false positives with a never ending search.
Check your server access logs (as suggested by @J.D.) for those specific dates you may find a link similar to this :
checked parameter it contains the name of the plugin that is requested to be deleted.
If you suspect it was a visual editor plugin then you should look for left over shortcodes used commonly used by these kind of page editors this will give a hint about the plugin that was installed. If it was not page editor plugin then you may still find broken shortcode left over (only if this plugin was providing any shortcode)
Some complex plugins make new custom tables in your database which are not deleted even after uninstalling the plugin. There you can check for tables that are not currently available in your plugin list.
My suggestion would be to get the backup from hosting company and compare your plugin list with that backup.
Best of luck.