So, original query is:
SELECT * FROM thereferences WHERE keywords REGEX 'ocean solutions' AND NOT (notes REGEX 'ocean solutions vu')
Pay attention that notes are set to null for first two records. You should check it as well. Because almost any operation against NULL produces NULL - neither TRUE nor FALSE.
SELECT * FROM thereferences
WHERE
keywords REGEX 'ocean solutions' AND
( notes is null OR NOT (notes REGEX 'ocean solutions vu') )