I would start by unindexing the field and then looking in it to see if the data is there. Then I would go back in an reindex it. What did your log file say about the recovery? It is possible that it lost data and if so, it usually is documented in that recovery log file. Hopefully you have a backup to pull data over from that is missing. When this happened, was it on a FileMaker server or peer-to-peer network connection? Also, what version were you using?
I did the re indexing and it was still missing data but I did find out that
an earlier error today caused it.