> double click the layout
Yes. In the lower right corner, choose Project, then in that: Application 1 (or application name here) > Layouts, and double click a layout.
Probably just your cap's .persist file was corrupt, or wasn't saved properly, or something. It's just the file telling Construct what event sheets and layouts to open the next time you open your cap. You could even delete the .persist file without problem.
Hmm, always wondered what those .persist files were, they seem to get into everything like a small child. Maybe in v1 they could all be stored in the construct folder somewhere.