Or, if you are calling someone's cell phone, send a text. Just a quick "Hi Arthur, this is Slartibartfast. Calling to ask if you have seen the mice." Or whatever.

If you really need to reach the person, do both, especially if you are not sure their age. Younger people (based on my experience) tend not to listen to voicemails, and older people sometimes are not comfortable texting. This is less true than it was a few years ago, but can still be applicable depending on the individual.