i think the case worker might have meant it was not on proper headed paper
as i've worked for printing companies, i know, esp with the colour lasers now and editing s/w, its so easy to produce a document or certificate that looks real .
and your right, i've scanned every doc and cert i've sent to the embassy, and its really difficult to tell which is the original, i've even managed to copy my misses IELTS cert , even thou they've used anti photocopying/scanning techniques on it, (greenish colour, lots of gray scales) and if i had decent paper you wouldn't know which was the copy or original.
to others, always have a copy of anything you send, especially originals, you might never see them again![]()