Disabled Users Logon Attempt alerts coming through - but user doesn't exist

Disabled Users Logon Attempt alerts coming through - but user doesn't exist

Hi there

I have an alert setup for when a disabled user account attempts to log in

Today I'm getting alerts suggesting a particular user is attempting to log in, but when I search in AD, there is no trace of that user. Anyone any ideas why this might be or where i could look to dig deeper?

Thanks