How to remove an image from a PDF?

Hi all, 

I added an image into a PDF (for a work thing) and i now need to remove the image. 

For some reason, in one document, it is not letting me remove one of the images. (I added 2 images in 7 documents and have been able to go back and remove them all, but this one image in one of the docs)

and i cannot work out why! It is like Acrobat isnt reading it as an image? but i placed it there i should be able to remove it again. Any Ideas?

I have Acrobat Standard, i am in Edit PDF all text boxes have been made editable, the other image i placed became editable and i removed that one, but this one image isnt showing as editable and unable to be selected at all. I tried the more option to look for a background etc and it "detected none".