I understand you need to retrieve the values of your secrets in DevTest Labs. The first time a user saves a secret, DevTest Labs automatically creates a key vault in the same resource group as the lab, and stores the secret. DevTest Labs creates a separate key vault for each user. Locate this key vault in your resource group and you should be able to find the secrets and retrieve them.
Please check this key vault and see if it resolves your issues. If you have further questions, please let me know.
-------------------------------
Please don’t forget to "Accept the answer" and “up-vote” wherever the information provided helps you, this can be beneficial to other community members.