I can't speak to the object you're referencing but I have a solution for this issue that I have used many times previously.
If I want to search for records by account name for a custom object in which I can't search by account name to find related records... This is what I do in order to be able to search for those records:
- Create a custom text field, e.g., Account Name Searchable
- Check the External Id box
- Create a WFR with criteria as "TRUE"
- Set it to fire every time a record is created or edited
- Create a FU to input the related account records name into the Account Name Searchable custom field
The above is a specific example for a lookup to an account. Obviously switch out whatever is necessary for your use case. Additionally, I created this solution prior to Process Builder so you could use that as well.