yes, deffinatly, this is an act of robery, there was no signing at the begining and he should had told her he wanted money if he edited it.
what you can do now is go back to him and threaten him with a warning tell him to give you the files or you will call the police on him, if he refuses, call the police. this logo is your right, btw, didn't u save a copy of it before giving it to him?
oh, also never come back again to that shop, try another shop so that he relises his mistake.