How to check if an image file exists already

Hello, I am working on trying to make my script better. Right now, I am trying to loop through a number of images, but there will be instances where those images don't exist.

What I am looking to do is exception handling in essence, but all of the methods I have found online are not working for some reason I am unaware of. An example of a solution I found that is not working is:

function file_exists(name)

   local f=io.open(name,"r")

   if f~=nil then io.close(f) return true else return false end

end
However, even when the file exists, it returns false and I get the error message I setup "File Not Found". The code I'm using this in is:

if file_exists(GeneralImagePath .. "_GeneratedStageCounterSnapshot" .. _currentStage .. ".png") then

   scriptExit("Found File")

else

   scriptExit("No File Found")

end
If someone could either explain why this isn't working so that I may get it working OR give me an alternative solution that I could attempt I would be grateful.