Search around for a GFCI outlet and see if it is tripped. It could be buried somewhere. Are these in say the basement or garage? If so, they probably have a GFCI at the beginning of the circuit. WHen you use the load output of a GFCI, anything connected downstream from it is also protected, so if it trips, a lot of things could lose power.
If not, and it may take some searching to find it, then determining the first thing in the string is usually the one closest to the power panel. Not always, but often.