find (one) in
To locate or discover one in a place that belongs to them, such as their home or office. I bet you'll find Susie in this weekend—she said she has to finish a big project for class on Monday.
find someone in
to learn or discover that one is at home; to learn or discover that one is in one's office. I never expected to find you in at this time of night. Did you really expect to find me in on a Friday night?