BTW: I found out how to get rid of deleteable objects in a simple, foolproof way:

1. Create a new frame.
2. Check the Items > View Created Items option.
3. Ctrl+A all the objects in the original frame and dump them into the new frame.
4. Copy the events from the original to the new frame.
5. Delete all the objects at 0,0 in the frame editor as these are created by your events anyway.
6. Seek out your undeleteable object and make sure that you delete that from the frame. It'll vanish from the list, the way it normally would have.
7. Test new level and delete the old one.

I recommend trying that maybe towards the end of development, once you're trying to simplify things down and organise or if you have >2 undeleteable objects in a frame.