The Unicode character U+2028 is a "soft return", which will break the line (ie: causes the line to wrap), but doesn't end the paragraph (eg: paragraph spacing isn't applied, quadruple-clicking still selects the following text, etc). A soft return can be inserted by holding down the Shift key when you press Return.
As you say, the PowerFind Pro regular expression "\s" will match any kind of whitespace, including the soft return character.
You mentioned that a space appears as a tilde, but that's not the invisible mark for a soft return character. When you have Show Invisibles turned on, a soft return will display as a curved arrow:

- softreturn.png (11.5 KiB) Viewed 2710 times
The tilde invisible mark is used for non-breaking spaces (Unicode U+00A0) and looks like:

- nbsp.png (11.81 KiB) Viewed 2710 times
That character can be inserted by holding down the Option key when you press the Space Bar.
I hope that helps. Let me know if you have any questions.