Shorted 12V wire to GND in ATX power supply. Did I fry it?
Posting comments as an answer, since apparently it helped OP solve his problem.

Some PSUs have output short protection, some don't. Some would have survived, others wouldn't.

There's really no way to tell just from the info in the question. I've accidentally shorted some PSUs before and most of them have survived. It really will depend on the model. If it doesn't turn back on again then obviously something is damaged inside, possibly a fuse, but it could also be one of the output devices, in which case it'll be much harder to repair.

When I say "survived" I mean that most of the times when PSUs with output protection are shorted, they turn off, you power cycle it (remove its power input/disconnect the it from the outlet), and they will turn back on again if the fault condition was removed. I looked up this unit on google and apparently its a very cheap PSU, some buyers even received it with some parts of the wiring missing apparently.

I'd tell you to check the fuse but I think the energy in the PSUs capacitors would be enough to blow a component inside of it.