Deleting EMAILS from gmail app search?

[AC Question]

Recently I have emailed something to myself from my dad's phone. Unfortunately, I am NOT allowed on his phone and I recently found out that, his work gave him that phone. But the big problem is. After I emailed it, I deleted the conversation from his inbox (I did NOT send it to archive), cleared his search history and cleared his Google Chrome history. But now my email shows in his search box and i can't get rid of it. Let's say my email is "purpledaisies99excample@gmail.com". Every time I search "purpledaies99excample" in his search bar, <purpledadaises99excample@gmail.com>" appears in his search. But, when I choose to press it, it says nothining can be found from it. Please reply as soon as possible.
Remember: This is from the APP.

 

[Golfdriver97]

I think that sort of thing is saved to Google servers. I don't think you can do anything to get rid of it.