There are underbed boxes used to store linens. Hide things wrapped in bedding.
Measure to see if there is a significant gap between the back side of a drawer and the back of the furniture the drawer is in. You might find several inches. If enough fasten a box to the back of the drawer. You will have to remove the drawer to get into the box. But so will any intruder.
There may be a low shelf at the bottom of your night stand several inches from the floor. These are often too low to get a vacuum under so this space is often overlooked. Fasten a box under the shelf with an opening to the back.
If you have luggage in your closet put a bunch of off season clothes in the luggage and hide what you will with them. If discovered it will look like you made good use of the space storing off season clothes.
If you keep boots in your closet drop it in a boot and stuff the boots with old newspaper to keep the boots from bending over and making creases in the leather. If mom might borrow your boots skip this one.
Get a heavy garment bag to store some clothes you don't use often. Store the goodies in the bottom of the bag. Adding some shoes might disguise the odd weight.
Use a shoebox on a shelf.
Many games have lots of extra room in the box. But a game. Play it some. Grow tried of it and put it up on a shelf with your goodies.
If you have a bookcase you can hallow out some books for your goodies. With the advent of the internet many old encyclopedia sets have become hidey holes.
Lastly
Just leave your vibrator out some day when you are reasonably sure if will be noticed while you are away. Chances are if discovered nothing will be said. She will know you have one or more. She may have some of her own. If she does say something about it ask her if she would like to borrow it. That will likely end the conversation, you won't have to ever worry about discovery, and you know what to get her for Christmas.
