Based on https://github.com/10gen/mongo/blob/c5c3086dcae61481f80664f1de1dcd965aee2147/src/mongo/db/catalog/README.md#use-in-wiredtiger-indexes:

During reverse lookup we should check if the secondary is unique or not, because for unique indexes the keystring might be stored without the recordID appended.

Right now in reverse lookup we get the recordID from the keystring with decodeRecordId here, so that wouldn't work if the keystring doesn't have the recordID appended.

It's possible we could just get the RecordId from the KeyStringEntry struct though in all cases: https://github.com/10gen/mongo/blob/bbf84d93a5bb9a9aaa3d7a52acd14673772d4997/src/mongo/db/storage/index_entry_comparison.h#L126

Additionally, when we call getKeys we should check whether we should be passing in the recordId - if the keystring didn't have the recordID appended then I don't think we should pass in the recordId here either.