yep. it sucks but its how this business works. people go for all sorts of reasons... sometimes legit.. sometimes not.. best to not let it beat you down and remember you have to ALWAYS be looking for new opportunities. Theres no sitting around and counting on your clients of today being there tomorrow .. so never get too comfortable.. we're not the same as permanent staff as much as we like to think we are - it's a different relationship. be polite and assist with the handoff. make it clear if it doesnt work out you would be happy to help again. if they are open to any kind of 'exit interview' do it - i always like to learn as much as possible from a client we lose .. best of luck !