"Ich war heute nicht zu Haus."
"Ich war heute nicht zuhause." or "Ich war heute nicht zu Hause.", the latter being somewhat old-fashioned. "zu Haus" is somewhere between very old-fashioned and disused.
Sorry, but this is not correct. 'zuhause' is just an alternate spelling of 'zu Hause' (Duden recommends the latter) and 'zuhaus' and 'zu Haus' are just short forms. All of them are equally fine to use. http://www.duden.de/rechtschreibung/Haus http://www.duden.de/rechtschreibung/zu_Hause
:D Thanks!!! They will see your comment here, I will rereport back if the sentence pops up once again.