If you delete a contact record via the UI in LCRM, the matching constituent record in Luminate Online automatically is marked as Removed. If you then recover the deleted contact record from the Recycle Bin in LCRM the constituent record in Online is not restored. Please contact Luminate Support if you have this scenario occur.
 
Note : If you remove contact records in LCRM via the API(apex data loader, excel connector, etc) the constituent record in Online is not changed. You would need to manually remove all constituent records in Online as well.