Are you paying rent?
If I was your mother, and I was letting you live in my home, and I imposed some rules on you, and you agreed to them (by living there, I think you could say you agreed.

If you didn't agree, you should have left), and you broke them, then she has the right to punish you.
And if I was your mother, and I was renting you a room, I could impose some rules, but I don't think that what time you wake up would be one of them. The rules would be more like "no open flames, no pets without written approval, no noise louder than 60 db after 11pm, and you room needs to be kept clean enough that the Fire Marshal doens't complain."
Best way to get your stuff back: talk with your mom about the household rules. Apologize, be very contrite, and then draw up a list of reasonable rules and have both of you sign them. It would work in your favor if you offered to pay rent in order to prevent her from suggesting rules about your bedtime and waking time.
FWIW, my parents had an "up by 8am" rule this past summer. As long as it seemed ike I had gotten up, they were cool with me sleeping in till 9 or so. I didn't pay them rent, so if they had wanted to punish me for breaking the rules, they could have, and I'm not certain I would have any legal recourse, as Ia greed to their terms by continuing to live in thehouse.
If you really want to get your stuff back without making any concessions (the rule of reciprocity, suggested by Cialdini, says that you are likely to draw up a reasonable set of rules with your mom if you make a concession--one concession is likely to dra another. It also says you'll do even better at making reasonable rules if you send your mother a flower the day before, and if your first list of possible rules is somewaht extreme, in its bias towards yourself. Don't make it too extreme, like "I can do whatever I want at any time of the day or night with anything of yours or mine, and the house will belong to me, and your car too, and I can play with fire all I want to and you can't do anything about it." but more like "There will be no curfew." You will then concede to maybe agreeing to be in by 1am, and up before noon, with the option for extensions for extenuating circumstances.) then you should take her to small claims court. Personally, I'd pull a Cialdini...