Hello!
This FAQ doc has a lot of information regarding the expected behavior for site search. By default, HubSpot site search should return all HubSpot hosted content. It’s important to note that if you host your blog externally from HubSpot, site search will not index this content. At this time, site search is specifically for content that you host on HubSpot.
Are you blocking your blog from being indexed by search engines? If so, that will also block your blog from appearing within site search results.
A developer can also follow this documentation to manipulate the results that appear. Is it possible that the domain your blog is hosted on has been excluded?
Let me know if any of these possible explanations gets to the root of your issue!
Best,
Alex