How to find hidden files on an iPhone?

I'm looking to find files of any nature purposefully hidden. Here's the deal, I'm 22 and married to a wonderful man that treats me very good for 3 years. Hecis 30. But I'm not stupid and im not blind. He has a problem, I've already discovered and talked to him numerous times about. Do I think he'll change? Not really but i need to decide if I can accept it or I need to go on and leave, I have to have my proof. Hard evidence that he can't deny and I will need this for closure as well. So I'm not here for a lecture or what I should and shouldn't do. He has an email that I found he uses and it's logged onto his iPhone but somehow hidden. I can get ahold of his phone but are there any other ways I might be able to access deleted messages, and other hidden files. Cause it's apparent he has found how to hide this email address and I don't know how he has hidden it. I know there's a lot more that he hides and erases. Just looking for some tips on how I may be able to access these. He has the newest iPhone if that helps any. Thanks a lot for you help.

You could try opening the mail app and when it shows his inbox, at the top of the screen, it should say "Mailboxes", if not, click whatever button is in the top left corner. If he has multiple email accounts, choose the one you want to check. You should see a number of things like Inbox, drafts, sent, etc, but click trash and all the deleted emails should be there, if not, then he emptied the trash, and there is no way to retrieve deleted mail messages without getting pretty advanced. I hope I helped!

Just try “LongPathTool” This is a file finder program. Just download this program FREE and install it. After then type your desired file name in search option of the program and click the Run button, you will get your desired hidden file within 2 seconds.