IIRC, you use an iPad but what mail reader do you use .... ?

What’s a mail reader?

Damn, your using Apple products...this could get complicated. As for text, from a tech point of view, there are different types of 'texts', we need to be clear on what app your using to 'text' people. Are using using something like whatsapp or are you using the iphones own text messenger?

The most common problem is that the ipad and iphone have too many emails and text messages saved and as a result there is not enough memory left to properly display the email and texts. So firstly, check to see if both your ipad and iphone have lot's a emails and texts saved in them, if they do then delete the ones you can.

The next solution is related to how the ipad and iphone are setup. Depending how they are setup, it is possible that the emails and texts are saved on Apple's servers and as such there is a synchronisation issue between your ipad and iphone. This sync issue means when you ipad or iphone wants to communicate with Apples servers to show you the messages, because it's out of sync with that persons account on Apples end, it makes it look like all the content has been deleted.

Now, if the above is how your ipad and iphone have been setup, having a near full inbox of messages and texts will prevent any more information from getting through hence again it will look like the content has been deleted.

It gets more complicated from here on in but look at the above and see if any of it relates to your iphone or ipad.

An email client, email reader or more formally mail user agent (MUA) is a computer program used to access and manage a user's email.

AFAIK, the default for an iPad is Mail.

There are apps emerging that allow deletion of emails/texts once they have been sent, but only if they are unread. Once read, the recipient has their own separate "copy" on their PC/device and they cannot be deleted by the sender.

If they have "vanished" it's a problem with the app used for messaging. Google will show topics reporting the same problem.

My Mac does the same for an email account that was hacked and taken over by spammers. It won't download content that it thinks is malicious, which is why I questioned if the account that was sending the mail had been hacked

Be very cautious if there appears to be no script. It is possible to compose in white and write a code that could attack without notice. ​I got caught like that many years ago and wondered what my security was banging on about until it was almost too late.

If in doubt run your mouse over it to see if anything is highlighted in blue.