Yes, we have 6 indexers that are in a cluster with a cluster master.
We have 3 searchheads used for different clients.
When we restart one of the indexers, if we go in the DMC, in "Indexing Performance: Deployment"
we see there's a missing indexer, the one we restarted. Our searches return gaps in them.
To be able to search from that indexer again, in the DMC, we to go in "Setup" , although there we see all the indexers properly configure, we simply have to click "Apply Changes". Back in "Indexing Performance: Deployment", the missing indexer is there. And we can do searches on everything.