Looking on the internet deeply has found these results:

I will be in the office tomorrow is the most popular phrase on the web.

I will be in office tomorrow 112,700 results on the web	I will be in the office tomorrow 132,200 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
It doesn't look like this phrase is very popular! The search could not find any examples on the internet.	I'll stop by the office tomorrow, but is there anything you could suggest in the meantime for... It's been a pleasure seeing you, but I got a big day at the office tomorrow. Pete's not going to be in the office tomorrow. I'll be back in the office tomorrow afternoon. I want you out of the office tomorrow. I will come down to the office tomorrow, and I will explain it all. I'd like you to come to the office tomorrow for a little chat. But if the consul is not in Milan, how can he be in the office tomorrow morning?

I will be in office tomorrow

112,700 results on the web

I will be in the office tomorrow

132,200 results on the web

More popular!

It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

I'll stop by the office tomorrow, but is there anything you could suggest in the meantime for...
It's been a pleasure seeing you, but I got a big day at the office tomorrow.
Pete's not going to be in the office tomorrow.
I'll be back in the office tomorrow afternoon.
I want you out of the office tomorrow.
I will come down to the office tomorrow, and I will explain it all.
I'd like you to come to the office tomorrow for a little chat.
But if the consul is not in Milan, how can he be in the office tomorrow morning?