There could be a few reasons why your Snapchat says that someone opened your chat when they actually did not:
Glitch or Technical Issue: Snapchat, like any other app, may occasionally experience technical glitches or issues. Sometimes, these glitches can cause incorrect information to be displayed, such as showing a chat as opened when it hasn't been. If this is the case, the issue is likely temporary and may be resolved with a future app update or by restarting the app.
Delayed Notification: There could be a delay between when someone opens your chat and when Snapchat registers and displays the notification. It's possible that the other person opened the chat, but the notification took some time to appear on your end.
Chat Status Not Refreshed: In some cases, if your internet connection is poor or unstable, the app may not refresh chat statuses in real-time. As a result, you might see a "Chat opened" notification even though the person hasn't opened it yet.
Misinterpretation: It's also possible that you may have misinterpreted the chat status or notification. Double-check the chat status and make sure you are interpreting it correctly.
Account Compromise: In rare cases, if your account is compromised or accessed by someone else, they might open your chats without your knowledge. This could be a sign of a security issue, and you should take appropriate steps to secure your account.
If you notice this happening consistently or encounter any other issues with Snapchat, it's a good idea to check for app updates, ensure your device's operating system is up to date, and consider reaching out to Snapchat support for further assistance. Remember to protect your account by using strong passwords and enabling two-factor authentication, as well as logging out from devices you don't recognize or use.