I am sorry to hear that friend. Here are some tips:
1) Wait for the client to approach to you and ascertian how interested he is in your services. A genuine client will respect your time and can offer you contract even without a mockup, provided he is impressed with your track record and portfolio!
2) Donot try to pursuade a client over a period of time. If you get a feeling that it won't work out, opt out in the initial stage itself to save your precious time!
3) If you receive a project/contract, request client to deposit full or partial payment in an escrow account of your's as a safeguard. If client resists, look at his past record or feedbacks or any acquire any information that might help you to decide if he is genuine or not.
4) If you already started working on a project like you did in this instance and never got paid, there's nothing to loose, but to gain. Wondering how? I'm sure you must have uploaded your work to a link. Use that link as a reference for approaching prospective clients. This will be beneficial and credible!
As someone said: "true efforts get true results. keep persvering"
All the best,
Vamsi Krishna,
Marketing Consultant,
Netconsultingpalace,
India
Aol: lbuild2005
Msn: webconsultant4u@hotmail.com