You can use use this command
GET USER <username> BUDDYSTATUSDifferent buddystatuses are listed here -
https://developer.skype.com/Docs/ApiDoc/USER_objectBUDDYSTATUS -
0 - never been in contact list.
1 - deleted from contact list. (read-write)
2 - pending authorization. (read-write)
3 - added to contact list.
The other way is to use the following command -
SEARCH FRIENDS command which will give you the list of your all contacts. Now you can compare if the username you are looking for is included in that list or not.
Regards,
Mirje