In the Out-of-the-box topic: Order an Item, when a user types in the short description of an item, the virtual agent only returns catalog items, not content items.
Release or Environment
In Virtual Agent Designer, there is a "Script Variables" section which includes a variable: filter_tables with the following default values:
Tables specified in the filter_tables will not be considered by search, and sc_cat_item_content is part of it.
Per your need, modify the filter_tables values to exclude tables that can be searched against, e.g. remove sc_cat_item_content