i have tried the quiz for this lab and i had found the dockerfile normally in the directory, so please make sure you did not have remove the content and try again the steps carefully.
You can see in your screenshot that the Dockerfile is there. You go to webapp-color and then execute ls. In the output, the Dockerfile is visible.
But then, before executing cat Dockerfile, you go to the templates directory. Because of that, you obviously won´t find that same Dockerfile in your working directory anymore.