HI Quinn, & Viking
Here are the results to the testing I did.

I expected the result in the first test shown as the pilcrow in the find box is a character that does not appear in the document except as a marker for the invisible 'return' character. As a marker, it is not searchable using that 'real' character as the search key.
I leaned toward the \n, as memory says that has worked in the past. But, as can be seen, it did not work this time, or for a different Pages 5 document which I tried before sending my previous reply.
For the third test, I selected the 'return' character marked by the pilcrow indicated by the left pointing arrow.
As can be seen, the first instance 'found' (marked by the yellow tile with a blue dot) is a space, and Find located 694 other spaces (marked by grey tiles with the same blue dot) in the rest of the document. Not what was being looked for at all.
@Viking OS X: My initial quote from your post was to draw docfi's attention to what (s)he entered in find (/n) to what you had said in your post ( \n ). The part of my post following that was a report of the behaviours, some of them unexpected, of Find on my Mac, running a specific version of Pages.
@Quinn:
Thanks for the check. Those are the results I would have expected on EL Cap as well, especially as I think that did work some time earlier.
Regards,
Barry