are you sure it is a font?
sometimes you can drawn it with a brush.
some fonts can be found on special websites.
http://www.fontspace.com/brain-fonts/yes
http://www.fonts101.com/fonts/view/S...ing_Federation
http://www.1001freefonts.com/
if you found it on a webpage maybe you can found it if you use firefox developer tool inspect element .
certainly others will give you better help.