It appears that it was not wired properly to begin with. Isn't there a way to simply wire the second half of the outlet?

Outlets by default come with the two sockets connected together, so that one connection is all that's needed to power both. However, it's possible to remove the part that connects both socketsl so that one socket can be wired to be permanently on (like a normal socket) while the other socket is switched on and off by a wall switch. So the first thing to consider is whether the outlet that is not working is connected to a wall switch, and if so is the switch on? Also check the circiut breakers. If you want to elminate the switch and make both sockets permamently on, you can disconnect the old switched feed and bridge the permanently-on hot lead to connect to both sockets.

Thanks,That's what I did. I just striped some more insulation and bridged between the two screws on both sides.

So prior to the fix there were no wires connected to the socket that didn't work, right?