Custom columns are not searchable unless they are configured to be indexed. If you’re building custom columns and want to search them in the future, the fastest solution is to create them as site columns—which are indexed automatically. If you’ve gone too far for this option, you can index the custom columns by adding them to an established managed property.
Add the custom columns to an established managed property via Central Administration > Search Service Application > Managed Properties. Create a new managed property and link it to the column/s. Make sure the managed property “searchable” option is selected. Once this is completed, a site crawl is necessary to include the newly-indexed columns in the search results.