Can someone get past authentication lock if they know my passcode?

you can just bypass authentication lock with a passcode?

No, you would have to enter the correct Apple ID and Apple ID Password first, then enter the passcode.

You cannot bypass the Apple ID and Apple ID requirement, and just enter the passcode, if that is what you are asking.

If you can't use your passcode to unlock the phone, these Support article statements are a bit confusing.

Mark a device as lost in Find My on iPhone - Apple Support

"For iPhone, iPad, iPod touch, or Apple Watch, you can also turn off Lost Mode by entering your passcode on the device"

If your iPhone or iPad is lost or stolen - Apple Support

"When you mark your iPhone or iPad as lost, your device is put in Lost Mode — it's locked with a passcode, payment cards and passes that you use with Apple Pay are suspended, and you can display a phone number and message for someone who finds your device."

How to remove Activation Lock - Apple Support

"Remove Activation Lock on the device

Follow the onscreen steps to enter the Apple ID and password you used to set up your device or your device passcode"

They would need your Apple ID and password which is different from the iPhone passcode. So, it is very unlikely that anyone would be able to get into your phone.

This might save you some time.

Bottom line.....no matter what button you might see on the Activation Lock screen, you cannot bypass Activation Lock with a passcode.