Search Drupal source/plaintext?
You want to use the Scanner module:


  Versions 5.x-2, 6.x, and 7.x of Search and Replace Scanner can do
  plain text search-and-replace, or regular expression
  search-and-replace, against the title, body and text content fields on
  all nodes in your system. This is useful for finding html strings that
  Drupal's normal search will ignore. The module is very handy if you
  are fixing typos in a lot of content, changing the name of your
  company, or are changing the URL of a link included multiple times in
  multiple nodes, among other things.