Over at the Technet Magazine blog, they've posted a very useful article that explains how to search for special characters like line breaks, tabs, or even white space. All you have to do is use a special modifier in the search box.

For instance, if you wanted to search for a word with a tab character in front of it, you could use ^tWord or something similar. Here's a few of the entries from the table:

Hit the link for the full list of special characters.

20 Helpful Search Strings for Finding Special Characters in Word [Technet Magazine Blog]