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

No.

There is no loss or theft coverage for headphones.

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

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