It would depend on the particulars of the contract signed before the work started. Have a look-over for clauses regarding deliverables and ownership your answer lies in there.
Worst case scenario, call up a lawyer, use the free consultation and see what can be done from there. Outside of rather large and very professional corporate firms (in which this kind of thing does not happen) most of these smaller players do not have much, if any expertise in legal and an angry sounding letter from a law firm would generally suffice.
