...well, i was assuming he had paid for it of course, and as such, paid for artwork is then client artwork, entitling the client to master copies...
...get a house built, you won't get master drawings without paying for them, go to the supermarket fill up your trolley and walk out saying "i will pay you later"...
...not paid for yet? send a printed proof, or a secure pdf, or a rough low res bitmap file (the client can probably use this on a website, if the client does, he doesn't own it yet)...
andrew