so the only thing holding the patch in is the primer?

I suppose that might work, for a while, maybe for the life of the house
since it's not likely to get bumped into up there on the ceiling but this
isn't what I'd call a recommended method for patching drywall.

The correct way would be to use any of the techniques for patching drywall
cited in a thread that appeared a few days ago, with the piece of textured
wallboard that fell out if it's in reasonable shape. Depending on where the
hole is, how big it is, the condition of the patch, etc. etc., I'd decide on
whether or not to to try and add some texture to it to match the surrounding
area. Sounds like in this case it's probably not worth the trouble.

hope your method continues to work
ml