Here you can see all events logged. If you are developing and log records they will be visible here.
"System configuration" => "Audit log"
From audit configuration you can choose what basic objects changes should be logged
For older records deletion you have to be running workflow cronjob
How to search for specific object modification/deletion?
You can search for objects modification by searching by category
CannedMsg- canned message modification
CannedMsgDelete- canned message delete event
AutoResponder- Auto Responder modify event
AutoResponderDelete- Auto Responder delete event
Subject- Subject modify event
SubjectDelete- Subject delete event
If in search you provide Object ID you can see exactly what modified object.
How to log custom events from extensions?
If you are developing extension you can log something there like this
erLhcoreClassLog::write(print_r(array('just some data to log'),true),ezcLog::SUCCESS_AUDIT,array('source' => 'Bot','category' => 'invalid_username','line' => __LINE__,'file' => __FILE__,'object_id' => $chat->id));
Required permissions to see log
Required permissions to configure audit log