You can't revert back to what Editable Mesh was before if you didn't convert the model to Editable Mesh in the same session (you could by using CTRL+Z).
But Editable Mesh is the most basic level of geometry so there's no reason to go back to anything since it won't be exportable by the script.
If the part you want to attach from another model doesn't require deformations you could just skin the entire model with one bone (or just attach the model to the bone using SELECT AND LINK option but I don't know if it's working).
If you go back one level beneath the skin modifier and edit the model by removing some polys or vertices you actually are changing the numeration of the vertices. Maybe that's why it's not exporting properly.
You can't revert back to what Editable Mesh was before if you didn't convert the model to Editable Mesh in the same session (you could by using CTRL+Z). But Editable Mesh is the most basic level of geometry so there's no reason to go back to anything since it won't be exportable by the script. If the part you want to attach from another model doesn't require deformations you could just skin the entire model with one bone (or just attach the model to the bone using SELECT AND LINK option but I don't know if it's working).
If you go back one level beneath the skin modifier and edit the model by removing some polys or vertices you actually are changing the numeration of the vertices. Maybe that's why it's not exporting properly.
Show some images, that might help.