So if you get the shelter, better get the large one! You will be a POPULAR person when that radio goes off!
I wouldn't worry about being found in the shelter - if your house did collapse and bury the shelter with debris, remember you'd be in the debris if you were in an interior closet. I'd rather chance being alive in the shelter even for a day or so.
Now something else to consider buying. If the door is narrow enough to fit between the car's wheels, it could be installed in the garage and double as one of those pits you see in garages sometimes to change oil!