I see that this is an old post, but I have the same problem. The bluetooth toggle can be switched off/on, but it just searches. The phone never discovers any devices, nor can it be discovered from a computer.
The phone have signs of falling to the ground (dents), but it doesn't look like it has been opened before.
Where is the bluetooth antenna placed? Is it a connector that can get loose by dropping it? I have tried searching, but I don't find any guides fixing the bluetooth antenna.
I have tried resetting everything and I have done a full restore in iTunes. No help.