There is always the chance that the indexer made a mistake or that there is more on the record than is in the index. If the originals are gone as sometimes is the case, then the index is all we have. And occasionally an indexer will add information to the index that's not in the original record.
But no matter the situation, you should at least ask yourself:
how do I find the record that this index indexes?
Failing to ask that question could be your problem.