I think if it is sent to a centralised exchange they can actually recover it but otherwise you should forget about it. That is why you should always be careful with the people you make transactions with.
No, I don't think it is possible to trace stolen Bitcoin except you know the person who stole it.
This is actually difficult due to the anonymous nature of Bitcoin.
If your Bitcoin get stolen, I believe the Thief would not hesitate in converting it as soon as possible.
It is not possible to track a stolen bitcoin because once it has been stolen it has been stolen and there's no way you can get it back except if you have the keys.