I received an AI file that needed the text to be edited, but I noticed that all that should be text blocks became single lines and sometimes single characters, (see attached image).
That can happen if the file was created in a previous version of Illustrator or if the Illustrator file was saved as a PDF.
This doesn't always work so proofreading would be needed, but if you select all the text blocks with the selection tool, cut them, and then select the Type tool and paste the text, it often pastes as a single block of text.