Yes. Unless you had a written contract with this artist transferring the copyright of the t-shirt design to you, then you only own the particular t-shirt/artwork you paid for, but not its copyright, which means you can't reproduce it, sell copies, etc. Those "full rights" of the copyright belong to him, since he created the work, and they MUST be transferred in writing under the Copyright Act.
Your ideas and inspiration aren't copyrightable interests, but you do own (if you created it) your graphic, which you're free to reproduce.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.
You seem to be saying two contradictory things. If you simply provided "inspiration" for "the graphic" or the basic idea, the copyright in the artwork probably belongs to the mall artist. On the other hand, if you actually "provided the graphic" and the mall artist simply transferred your graphic from a paper medium onto a t-shirt-- i.e., by painting it onto the t-shirt-- then you may well own the copyright in the basic artwork.
You really should consult with a copyright attorney to go over the details and see whether you have any rights. It doesn't sound hopeless, but no clear answer can be given on the facts as you have stated them.
Disclaimer: This answer doesn't establish an attorney-client relationship or constitute legal advice. It is for general informational purposes only.
Ms. Bass has keyed on a critical issue, above. You say that you provided the graphic for the work that the airbrush artist put on the tee-shirt. If that is the case, then why can't you simply reproduce your original graphic instead of the work that the artist made from it. If the work done by the artist is sufficiently different from your original graphic that you see value to reproducing it instead of your original graphic, then your question is answered for you. If the artist added something (pretty much anything) to your graphic that you feel has value, then the artist has clearly contributed copyrightable elements to what ended up on that tee-shirt. And, if that is the case, then you need a license in order to use that work beyond the limited use on that single tee-shirt.
However, you might want to dig up any receipts or documents you may have gotten when you paid for the artist's work in the first place, as there may have been some form of license on there that you have already entered when you made the initial purchase. You'd definitely want to check the terms of any such existing license so that you know the exact scope of what you already paid for.
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