If the cables were actually cut, they've made you job easier.
Even the relatively inexpensive 'data/phone' type tracers (for use on un-powered lines, about $120) will read through walls, etc.The #701K in this link is truly the 'classic' for this use:
http://www.lashen.com/vendors/tempo/toners_probes.asp#pe701kFor more demanding jobs, for live circuits and even some underground work, this tracer (508S) is useful:
http://www.lashen.com/vendors/tempo/cable_locators.asp#pe508s It's all a matter of being systematic andpatient. First ID -colored masking tape works great - the receptacles that are working. Then apply the toner to the dead receptacles - I use a plug with a pigtail for this.
The tape ought to give you a very good idea as to what circuit and what area of the house has the break. Use the toner to follow the wire from what you think is the first dead receptacle in the series; when the signal stops, you have your break.
It also helps to know the story behind the problem. For example, was the damage done bofore, or after, the walls were closed in? Was it deliberate or accidental? Could it be something as 'simple' as a wire not connected at a wire nut (something I have found a few times)?
Indeed, my very last service call before leaving Reno was this exact situation - and it was a loose wire at a wire nut. My being systematic made me look like a genius when I found the problem in the very first box I took apart.
