Phrase or expression for "sending a message to the wrong recipient" in chat

Solution 1:

This can be called a mistext

From Slangit:

A text sent to the wrong person A mistext is an accidental text that is sent to the wrong recipient. It usually is sent to the person that the text was about, which makes the error even more awkward.

Mistexts are usually the product of a person who is rushed and carrying on conversations with other people at the same time. They result in a textastrophe or textmergency that requires further explanation from the sender/perpetrator.

Example "I got a mistext from Jess the other day and she was throwing major shade at me."

Solution 2:

Misdirected text is the term I'm seeing online. For example an article by CNET on a patent by Apple entitled:

Apple aims to prevent misdirected text messages

An article on boredom therapy:

Everyone occasionally texts a wrong number accidentally. The recipient of these misdirected texts has a few options: they can politely point out the mistake, they can ignore it, or… they can hilariously prank the poor person on the other end of the line!

Unlike the notion of a butt dial which means you dialed your phone accidentally, the misdirected text requires actual user error.

That said, I've heard people try to connect the phrase butt text or even using butt dial for when a string of characters you didn't intend to send goes out.

People also call this an accidental text and if done on purpose a fake accidental text.