I don't see the tickets of a contact when I search using the email address

When you search using the email address of a contact, there would be 4 categories by which the search results would be split. Only if the email address is present in the body of the ticket would it be displayed in the 'Tickets' category of search. However, if you are looking for tickets created by that contact, you need to go into the profile of the contact by clicking on the 'Contacts' section and find the ticket.