If Gmail search does not return any result that means you are searching in wrong way. By default gmail search does not return results from trash or spam folder but you can search result in these folder where you need to type different expression in search box.
For search in trash and spam you need to type “in: anywhere” to the search expression. if you want to search in trash you can type “in: trash” in search box.
Follow the process to search in spam & trash folder as given below:
• First, open your Gmail account.
• Next, in the search box from the top of the page, click on down arrow
• In search you need to select spam & trash.
• Type the information in the box which you are finding.
• At the bottom of page, click on search search.
Finally you will get search email in your spam or trash folder.