I was wondering if there was any way of requiring that course reserve materials checked out from the Reg should have to be returned at the Reg? It seems like the purpose of a short loan period is to make the material available to as many students in the course as possible, and having a book unavailable for anyone while it is "in transit" between libraries does not really support that goal. I understand that all students are busy, but I think requiring students to take an extra ten minute walk to return a book so that another student can use it makes more sense than having a book in transit between locations for 3 hours or more. I don't know if this is feasible, but it seems really reasonable!
We couldn't have said it better ourselves, and do ask that patrons return reserve materials to the locations where they checked the material out. (see: http://www.lib.uchicago.edu/e/using/borrow/).
Admittedly, the problem is enforcement. We usually don't levy fines for materials returned to the wrong location, because our system is programmed to stop the fine clock (so to speak) once a book is checked in at any library. Transit time, if any, back to the shelf isn't counted against the patron.
This being said, we could certainly fine people for the time a reserve book spends in transit. (3 hours would be on the fast side -- sometimes we can't ship books immediately.) Another option would be to notify the instructor, especially if the "stuck in transit" problem occurs frequently with a specific book.
Both of these options, however, are rather big guns to fire: overdue fines -- $1/hour -- would rack up quickly, and instructors often come down pretty hard on students who appear to be obstructing use of reserve materials. If you notice a specific reserve title frequently "in transit" please tell us, but otherwise we're inclined to assume that someone just made an honest mistake.