This reeks of a loose connection. Wires never break (generally), so the break between the source (breaker panel) and the outlet will be wherever the wire has been broken for use. Take a voltmeter and measure voltage at the breaker's output (note: be very careful as this requires removing the breaker panel faceplate, exposing a lot of wires that, if touched, will be pretty exciting, but you only get to do it once...). Then determine the next point of contact (usually the first receptacle), and measure voltage there, if no voltage, take it out and measure voltage on the "feed" wire. Eventually, I would bet you would find a wire that has some carbon burning. Fix the bad connection, and your vacuum will suck again.