Although i'm not answering your question directly i propose two other approaches to modify forms.
1. Directly within designer i.e. you may even copy paste the content you have prepared. It is a small icon that appears when you select and hover a human task on your bpmn diagram, that looks like a person. If you click it the code of the ftl is presented and rendered real time as you edit it.
2. If you go within guvnor to the assets of your package i.e. defaultPackage, and select "open" for the specific form, a page is shown with download and upload fields.
Most likely your form was archived. In Guvnor to completely delete a versioned asset is to archive it first, then go to Administration tab -> Archive and permanently delete it there. Currently in Guvnor with its REST api that jBPM Designer extensively uses for communication with Guvnor, archived assets are _still_ parts of the packages (are seen as such) unless you permanently delete them.
Also check out the live-preview form editing in jBPM Designer here: http://surdilovic.wordpress.com/2012/08/06/process-and-task-form-editing-in-jbpm-designer/. It allows you to catch possible errors and preview your form as it will be seen by your users.
Hope this helps.
Thanks for the tips! I will try these out.
I'm trying to archive then delete the .ftl file in Guvnor.
When I check the .ftl file and choose Archive, the entire package gets archived, and not just the checked file.
Is there anything I'm obviously doing wrong?
Open the asset first (select form and click open button), when File-Archive.