Speaking ASA, if the umpire is engaged in other duties (substitutions, injuries, etc.), the pitcher is allowed to exceed the normal allotment of 5 (or 3 for SP). There's nothing in the book that says they HAVE to use F2 to catch the warm-up pitches, but I wouldn't feel right allowing another fielder to go behind the plate without the proper protective equipment. Personally, I think you'd be justified in prohibiting such action.
IF NCAA doesn't allow extra warm-up pitches (meaning "that's 5, and that's it, period.") when an umpire is engaged elsewhere, then I'd say what you did was merely preventative umpiring. Someone else will have to clarify that, though.
Oops, someone already did.
