The forwarders will continue sending information to the main indexer one they are put back online. I had the same situation with some dormant forwarders. Once they were back online they refreshed all of the data from the last event that was available. Takes a wee bit of time based uupon the quantity of data. Do you specfy an index for your forwarded data? It is easy to verify when your configure your data inputs to use a specific index. Otherwise review your data inputs and check the default index used. YOu can search that indexfor the missing frowarders data easily.
