Have you considered making sure that the filter overlay that was created is not a linked file now? If it is, try embedding the file. This may allow you have an editable file.
if you are seeing a preview of the image when you open in Illustrator then hopefully all is not lost.
Look at the file in outline mode and if you just see a black square, then hopefully if you embed the file it will release, and allow you to make edits.
Master newbie.