Lost and Found in Active Directory ?

To understand Lost and Found concept, consider below example from my test lab.

I have two Domain Controllers (DC2 & DC3) in two different sites. Dc2  in a site named "Delhi" and Dc3 in "Pune" site. Replication schedule between both the sites are configured as 15 mins.

Note down below operations -

1. Now I have an admin who logs in to DC2 and move a user named "Abhishek Bansal" from Users container to an OU named "TestOU".  Since it's a change so it will be replicated to other DC's in the environment. As per schedule set it will be replicated to Dc3 in/after 15 mins.

2. Before change done in step1 would have been replicated to Dc3, some other admin logs into Dc3 domain controller & deleted "TestOU", meaning at step1 there is a change of moving an object to TestOU and at step2 someone deleted that OU before that change would have been replicated.

So the result of these operations will push user "Abhishek Bansal" into a special container called "Lost and Found".

So to sum-up, We have different kind of conflicts in Active Directory replication. One such type/kind of conflicts is Lost and found. It occurs when one update is putting an object in a container & before this update would have been replicated to other DC's  , there is one more update from a different DC which is deleting that container, as a result the objects that are moved in update 1 would be moved to a special container called "Lost and found". 

To view lost and found container under dsa.msc, you need to enable Advanced features by simply navigating to :  View --> Advanced features