I dropped my iPhone 4 in the toilet for literally 3 seconds, dried it off with a towel, and it was actually lit up and working, so I thought I had just cheated my poor phone's death when all of a sudden it went black. It continued to vibrate when receiving messages and then began to vibrate every few seconds until it stopped working completely. I quickly put it in a bag of rice and the liquid indicating sensors don't seem to be activated but it still won't respond or be recognized by my computer. Is it time to give up or should I be patient and give it more time? If so, how long is long enough to know that it has reached the point of no return?
The liquid sensors are only there to determine if the device is still good for warranty, they're placed in strategic spots where the Apple so-called "geniuses" can quickly look and tell you that your device isn't eligible for warranty anymore (even if your problem happens to have obviously nothing to do with water damage).
In fact, the places where the liquid sensors are located on your device (dock and headphone connector) aren't that vulnerable to water and you can usually wipe whatever liquid is in them and the device would still work. This has changed with the iPhone 5 though, and the liquid contact indicator is now inside the SIM tray, which is tightly closed and water is unlikely to get inside accidentally (you'd need to completely submerge the device, in which case it'll completely kill it).
If you happen to be lucky and your device is still under warranty I suggest you go to an Apple Store, you'll get it replaced immediately.