If you assigned an "online only" conditional tag to your snippet placeholders, and your Printed Documentation layout has a "NOT Online" Conditional Build Expression, that might be the cause.
I just tested this on a single topic whose only content is a snippet (other than an H1 heading) from an existing project (with no conditionalizing), and everything appears in the DOC file. Granted, I'm using RH 8, but I can't see how RH 7 should be any different.
I do actually use conditional tags and snippets quite a lot in our
documentation so I am familiar with the "Print" and "Online" tags. I don't
know about RH8, but RH7 does not allow you to set a a conditional tag to a
Snippet at all.
I just created a blank topic and inserted the snippet which is not being
printed, same result. I then created a new snippet and inserted it into the
same topic, it printed! Curiously, if you double-click on the new snippet
placeholder, it opens for editing however, doing the same to the rogue
snippet placeholder, it does absolutely nothing however, it will open if you
select Edit Snippet. The answer may be a corrupt snippet but it shows no
other evidence of problems other than it will not print.
Ahhh, snippet corruption. That's what's wrong with the world, today!
Thanks for the smile, Leon!