How can you create a process model from an instance? The process model for proc

How can you create a process model from an instance? The process model for process instance is deleted and I need to recreate the process model from the process instance. When I open the instance of process model in designer (edit mode), it does not let me save it nor it let me save a new version. I get an error as below when I try to save a new version
"This process diagram could not be saved due to the following errors. Please correct them before continuing.
Unable to locate the process model. It may have been deleted."

OriginalPostID-150574

OriginalPostID-150574