No hot wires?!

I am replacing the outlets/switches in my bathroom. One receptacle has a light switch and an outlet. I used a meter to determine which of the 3 black wires was my hot one, then hooked up the devices accordingly. 6 inches away is a double switch, controlling a light & exhaust fan. There are 4 pairs of wires in this box, and NONE of them test hot! Both outlets are on the same circuit. If 2 wires were hot, I'd connect them to one side & break the tab, right? I've tried turning the breaker off/on, pigtailing all the white wires, connecting the other outlet first....I've got no power!

I don't know if it's significant, but when I first took off the cover, one of the fixture wires had the insulation removed an inch from the end, and the wire was looped over the first screw before the end was attached to the second screw (on the device side). When I first tried replacing the switch, I put the wires back exactly as I found them (or so I thought), but then activating either switch turned on BOTH the light and the fan. So there was power going to it yesterday! I took it apart to try to separate the fan & light operation, which I assume had something to do with the middle-of-wire connection. Now I kind of wish I'd left well enough alone...

Why are none of these 4 wires hot?

Tried again today, and the voltage meter seems to randomly beep. It doesn't seem to trigger on any particular wire--at least not consistently--but it does appear to to have some correlation to when I get next to the metal junction box.

could you have a gfi plug in that room or somewhere else on the same line. if the breaker blew, it may look like it is on but must be turned all the way off before it will turn on. My guess is the power comes in the double switch box the for wires might be fan ,light power coming in and power going to the first box.
If that is correct you would have two pig tails and two blacks tied together the pigtails would go the fan and light switches and all whites tied together.
Either way it sounds like you have one extra wire unless you have swithes for two seperate lights

The light/outlet combo that is next to the problem switch had 3 sets of wires, and it works without problem. The double switch has 4 sets of wires; I assume two power inputs, one light and one exhaust fan. But none of them have juice.

If the other receptacle was downstream, it wouldn't work because these wires are disconnected, right? If the other receptacle is upstream, then I'm thinking that once I connected the wires in that, the wires in the second one would go hot.

But no hot. :-( There is one gfci in my other bathroom; it wasn't tripped, but I reset it anyway.

When you say "voltage meter" are you referring to an inductive tester, or "tic tracer"? These are nice little tools but are not always reliable. When you use these you should always test them on a known hot, such as a receptacle that you know is on. Some have sensitivity adjusters on them too, so that could also be your issue. It would also be a good idea to have a regular voltmeter as a backup. Hope this helps.