Finding ceiling joists can be rather confusing, but trust me… they ARE there, and since they hold up your whole building, I’m sure they’ll be able to take the pressure of a pole. If not, there are much, much larger problems going on there!
Depending on your ceiling, finding them can be anywhere from super easy to crazy difficult. I have stucco ceilings (which I hate!) and they make the whole process much more difficult, because it can give false readings- in either positive or negative. I’ve also had ceilings made of thick wood board, which causes the stud finder to have a constant positive. I could basically have put my pole literally anywhere on that one, but I chose to get a longer screw and put my Lil Mynx under an actual joist, just to be certain.
There are some clues you can look for- if you take a step back and look along your ceiling, sometimes you can see “which way they run” by seeing how your ceiling might dip and undulate. You can also take some lights out of the ceiling and stick your hand in there and actually feel around for them, too.
Keep at it, though. Not all stud finders are equal, and sometimes it just takes a little extra testing to find a good one!