I'm not sure what to make of this, Andthencraigslis. I don't think there's any reason you shouldn't be able to call him. Being too tired is a pretty poor excuse when he is at home.
Do you know your neighbors well enough to ask if they have seen any strange cars in your driveway/on your street while you are at work? Is it possible he could be going out somewhere, and that's why he wanted to be texted instead of called?
It's really hard to say. I know at times we can be paranoid, but when our gut is screaming that something is wrong, then it's usually best to investigate. It's okay to lay down your needs with your husband, too, about about being able to contact him by phone at all times (except for maybe during work meetings, etc.)
Best of luck to you, and keep us posted...