Resolution:
Lost and Found messages are exchanged between RVRDs running in the same local network, usually redundant RVRDs.  For example, rvrd1 and rvrd2 (having the same configuration) are two RVRDs running in networkA.  If rvrd1 is up and later rvrd2 is up, rvrd1 detects the presence of rvrd2 servicing the same local network, and it reports a message "Found rvrd2 in networkA".  Similarly, if later for some reason, rvrd2 is gone, rvrd1 detects the absence of rvrd2 and reports a message "Lost rvrd2 in networkA".

Frequent lost/found messages will appear if the network is unstable (for example, a faulty network card or cable connection can cause the network to connect/disconnect many times in a few minutes).  If the RVRD machines are consuming a lot of CPU and memory resources, you can see frequent lost/found messages together with frequent DATALOSS messages.