How to find and connect lost email to my ticket?

CRM > Tickets. There on top left corner blue text "Tickets" with arrow down. Search bar click & Type "Emails". Keep all emails open > no specific filters and in the little white search bar just above the name of email > paste the name of ticket in there. If more then one email with the same subject arrived I would double check the creation date of ticket to match the creation date of email.