What happen if I receive a message saying my Apple ID is locked because of two unauthorized devices even though I only used one?

As noted already, those are phishing attempts. Scams (e-mail, text messages, and phone calls) are getting very good at closely imitating true Apple communications. Always be cautious. Here are some guidelines:

Identifying legitimate emails from the App Store and iTunes Store - Identify legitimate emails from the App Store or iTunes Store - Apple Support

Recognize and avoid phishing messages, phony support calls, and other scams - Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

Apple 'How to identify, avoid, and report phishing' video--> https://youtu.be/SR3Z3fXXjfw

This is a scam message and is not coming from Apple. Please delete it and don't click on any link in this message.