Bruce had been wandering through the TARDIS, completely in awe about the whole thing. It had a water park, and a zoo. Though he had yet to find the zoo. He was determined he was going to locate it, and that's exactly what he was looking for when he ran into Owen. Very literally almost ran into the man.
"The Doctor told me there is a zoo here," he explained. "Jack said the TARDIS could lead me to something if I wanted it enough, or if the TARDIS wanted me to to find it, but... apparently neither of these things are happening at the moment."
Which really wasn't surprising to Bruce. Out of everything he'd learned about the TARDIS, the fact that it was able to lead him somewhere wasn't the most impressive thing about it.
Bruce was not at all concerned about the fact that Owen was his guardian. Of course, he didn't know the man well. There were enough people living in the TARDIS that Bruce was likely not going to get into too much trouble. Especially if the TARDIS decided to keep him out of trouble.
Though that was only if Bruce remained inside. The TARDIS couldn't protect him from, say, Fight Club.