You should have 2 wires on the alternator, (not counting the ground wire).
The heavy gauge red wire to B+ and the warning light wire which goes to D+.
The warning light supplies the excitation current to get the alternator charging.

No light = No charge.

You should have a light gauge wire emerging from the loom at the same point as the wire for the oil pressure warning light (just checked on mine, it`s red) if you ground this wire with the ignition switched on, the charge warning light should come on, as well as a load of other lights.
If you want to check the alternator, connect a 5W bulb or test lamp across B+ and D+ to simulate the warning light.
I think you have knocked the wire off the D+ plus terminal and it is now lurking behind or below the alternator where you can`t see it.
Find that wire and refit it, or run a new one and I`m sure all will be well.
Good luck,
Colin.