If I have applecare+ and I lost my airpod pros is there a discount in replacing them?

Did you elect to get the "Theft and Loss" AppleCare+ plan? If so, you may be able to get a discount. If not, then, Apple does offer replacements by using the following link: Replace your AirPods - Apple Support

No.

There is no loss or theft coverage for headphones.

AppleCare or AppleCare plus does not cover lost or stolen devices.