I was trying to update the "Forgot my password" email, but nothing was changing. When I scanned your code, I found that the functions
sb_we_lost_password_title were not being used at all. I'm not too sure how your plugin is supposed to be structured, but I just added the following code to the bottom of the function
add_filter( 'retrieve_password_title', 'sb_we_lost_password_title' ); add_filter( 'retrieve_password_message', 'sb_we_lost_password_message', 10, 2 );
If you could hook up those functions to the proper filters in a way that follows your plugin's structure, that would be greatly appreciated.