I recently had a paper rejected by a peer-reviewed journal, but the rejection notice gave no indication of where to find the reviewers' comments. I gather (from questions like this one) that it is customary for authors to get to see this information. So how do I go about finding it? Should I contact the editor and ask to see the comments?
Well, there isn't really anything you can do except ask the editor, since he/she is the only one who has them (except of course the reviewers themselves, whose identities are not and will not be known to you). So if you want those comments, that's what you'll have to do.
Of course, it is possible that:
the paper was "desk rejected" by the editor and never sent out for review at all; or
this journal has a policy of not sharing reviewer comments; or
the editor has decided for some reason that in this case it is not appropriate to share the comments with you.