Hi ganeshimpex,
I understand that it hurts to loose a positive feedback. However, had the buyer left you a negative or neutral feedback even that would have been removed.
The logic being that if a user is getting suspended within 90 days of registeration, he does not belong to the eBay community and thereore his feedback or transactions should not impact any member.
I hope this helps you understand ther eason behind the action.
Warm Regards,
Sapana