Logging of failed discoveries

While during our migration from SCOM to Solarwinds i've kept both set of alerts personally going to me.  That way i could compare and validate those items that would require action from others.  Trying to be nice and all.

Well today, i had an alert come in from SCOM that also come with a VMAN alert. 

So, the question is this.  Is there an easy, hopefully automated method, that can produce those machines/ips which were unable to be discovered?