Additional chat-related features and issues within Microsoft Teams for Education
Hi Kitty.1.1,
Welcome to Microsoft community! In Microsoft Teams, when someone sends you a message, you will see a notification about the new message, but if the sender then delete that message later before you read it, you will see a sentence under that people says "This message was deleted" (like below picture), and you will not be able to see that deleted message.
Given this situation and consideration your concern, I suggest that you may directly contact that recipient to explain your situation and confirm this.
Your understanding and cooperation will be highly appreciated.
Best regards,
Jennifer