In theory, all officers of infantry battalions were to carry whistles for the purpose of sounding signals (presumably in the event of the bugler being a casualty, unavailable or otherwise absent). They looked a bit like the traditional policeman's whistle but with two holes, which can be stopped up to make different tones.
I expect this is the shiny thing you can sometimes see hanging from the chain on the crossbelt of officers of the period. A lot of officers took a relaxed approach to uniform on campaign however, so I don't know if it was only a part of some regiments' uniform - the rifles, I think, had them - or if all regiments should have had them, but the officers didn't bother with them outside of a parade. Maybe they kept them in their pocket?
The calls that could be made were - attention (as in, look over here, not 'come to attention'), advance, halt, retire and assemble/rally.
Given that the bugler, if present and fit (and also, if he had followed the advice of "Spit boy, spit,") could sound these orders and plenty more (given the superior range of notes and volume), one would assume it would be fairly uncommon, but not unheard of.