To follow up, a solution may be to query my entire blog database, and then use vanilla javaScript to find a substring of the plainContent field.
When found, update a new array with matches, and then populate a repeater with this new array.
However, as the blog collection only support querying 100 results and these objects are very large, I am desperately trying to avoid this workaround. Its both slower, more fragile and doesn’t technically search the entire database, though the last 100 results would suffice.