Forms - Searching Data

Database description

I have one to many relationships between tables related with PersonID. From the entry forms I enter data and there is another form to search data. The data search form displays some 5 fields from different tables: first name, last name, phone, email...

Problem description
When I enter new data in all the above named fields, then the search engine can find and display the new record. However, when I leave blank some of the fields, let's say, the phone field, then the search does not display the entire row, although the first and last name, for example, exist in the appropriate table.

I would appreciate, if anyone could help me to solve the problem.

Thanks