You've got to remember that in most supermarkets, the photo guy is really just a general member of staff that knows how to use 'the photo machine'. Give them anything that isn't 35mm/APS film or .jpg digital photos and chances are they won't have a clue.

I have had problems in the past getting films developed, plenty of photos have come back with quality control stickers on them but that was usually down to using a cheapo disposable camera.