No luck with the Sindulfo Diaz quandry. No fight is mentioned for him in the New york times in that week.
The Benny Bass and Tiger Flowers bouts you mentioned are both listed in their records in the 1981 Ring Record Book - so they appear to be OK. Haven't checked the Petrolle one yet but fighting out of Fargo I wouldn't be surprised if one or more of his fights missed the big newspapers where I think many of the records have been put together from.