Unidentified FRBs in archival data

Recently Zhang et al. (2019) reported the discovery of FRB 010312 in a dataset previously searched for FRBs. Here we explain how and why this FRB was initially missed, and highlight several caveats relevant to FRB search completeness. It is possible that up to $\sim40$% of discoverable FRBs remain undiscovered in some existing public domain archival data sets. The situation could be even more pronounced given that FRB search pipelines generally look for temporally-symmetric broadband flat-spectrum pulses; most FRBs do not look like that.