In the Search Tips, which you can find under the search box on the Advanced Search page (here on AureaWorks), it says under "Search for phrases":
If you enclose a phrase in quotes, your search will return only content where the words in quotes occur next to each other and in the same order. For instance, specifying "black cat" will return text where this phrase appears exactly as quoted, such as "our black cat brings us luck", but will not return "the cat was hiding in the black box".
However even a search for "Search for phrases" on AureaWorks brings up results for content without that phrase:
I will also create a private case, but thought I'd post this for the benefit of others also experiencing this issue.