Sleezy as this is you wouldn't be able to show damages since you didn't sign the contract. The other lawyer can claim error and the burden of proof would be on you.
If you did accept, then you have a lengthy court battle ahead where a jury could very well rule "abide by the contract you signed you reneging moocher."
The real world isn't a school playground. Calling a teacher over is time consuming and expensive and far from a guarantee of justice. It is up to you to keep yourself safe from assholes like this by always doing your due diligence. Someone who pulls this kind of shit constantly will eventually lose their license, but many years down the road and after many victims.