My lambda function code suddenly disappeared

Hello, it is currently difficult to accurately locate the specific reason based on the limited information you have described. Perhaps you need to check Cloudtrail to see if anyone else has deleted your Lambda.

In addition, you can use Github or AWS Codecommit to manage your code, and use AWS SAM to help you building and running serverless applications on AWS. this way, even if someone accidentally deletes your Lambda project, your code is still safely saved and can be quickly republished to AWS