Microsoft SharePoint PowerShell - command let failed to get Group description and throw group object not found for the group doesn't having permission on site collection

Hi ,

I trying to get the single group from site collection and therefore i am executing powershell  cmd - 

PS C:\Users\Administrator> $FormatEnumerationLimit=-1;get-spsite "http://w2k12dc
-sp2k13:41868/sites/TestDeltaPer/ " -limit all | select -ExpandProperty RootWeb
 | select -expandProperty SiteGroups | where ({$_.Name -eq 'Group Test12'  }) | select  -property *

Command run successfully and result appears on the screen but the some of the fields value as blank(e.g Description). Is any specific reasons for that ? Description field value is more than 70 character is this causing issue? 

Second issue is when i execute power shell  command for the group which does not have permission on SharePoint. I am getting group not found error.  Why i am getting this error ? Also i able to see the group properties through command - $FormatEnumerationLimit=-1;get-spsite"http://w2k12dc-sp2k13:41868/sites/TestDeltaPer/ " -limit all | select -ExpandProperty RootWeb
 | select -expandProperty SiteGroups | Select -property *

Any pointer on this would be helpful.