Lost images in power point files in Microsoft office for Mac

Hi everyone - I am new to the site and also a bit of old duck with few skills in the tech department.  I have tried Apple help and Microsoft help and they say it is an application issue - and a file issue - respectively. 

I have a 60 page doc in Powerpoint that is at least 4 images to a page and the images have all disappeared (at once) giving me the little red cross and "the picture can't be displayed" message.  I have dragged and dropped and copied and pasted these images from all over the place - existing powerpoints, internet, screen shots etc - over several months - so whilst they  might be somewhere on my computer putting them back in order etc. is not a possibility.  My question is - has this happened to anyone else and can i fix it?