I agree with both ladies. I know you don't want to get into a lengthy discussion with him about it, but since the situation is different, it might warrant one. Being a very generous gift, and given the situation that you're not graduating just yet, I think it would be nice to talk to him personally and thank him, but let him know that since you're not graduating, you don't feel you can accept it. More than likely, he'll still want you to have it, but it will be nice that you were thoughtful enough to suggest the return, and that you did it in person (rather than a thank you note or e-mail). Just my thoughts... take 'em or leave 'em.

That was really nice of him to remember.