It's not a matter of hiding fabric and supplies it's a matter of not irratating him with yet more things to clutter the house with.
My dh is very frugal. He doesn not have hobbies that cost money and he doesn't really have a problem with what I spend on my hobby but he does give me the disapponted shake of his head when I bring in yet more fabric.
I'm a "it's on sale and I'll find a use for it someday" kind of gal and he's a "don't buy it until you need it" and then only buy what you need so you have no waste.
I've learned to stop spending and only buy what I know I will absolutely use. No more "hey, it's only $1 a yard. I'll buy it all now and someday find a use for it. Even if it's the ugliest fabric I've ever seen."
Plus I sew with a group and we receive a lot of donations so I bring home bags of fabric and supplies. He does not like to see the basement aka my sewing room, cluttered with bags of stuff. So I keep it all nice a neat-ok, I try and fail miserably. When I bring in more I just add to my colletction and don't mention it to him.