Yes, if you got the patience of a saint, you may try your luck at the borders without it, and some countries are more strict about it than others. I would think it´s a slim chance, though. Sorry I dont have info about West Africa in specific.
If your vehicle is stolen, you should immediately make a police report of the incident, and the carnet bond should be returned to you (in theory - luckily I have never had to try, if it works in real life!!)
I wouldnt pay any big deposit at any border, especially in Africa. High risk of not seeing that money again.