So you think-- this is a magic stationery case.
No--really! Hermione has one just like it (I think hers is green, though). Professor McGonagall lent it to her at the start of term.
See? Haven't lost a thing since-- this is a unifying case. Wouldn't you just love to have all the small articles of your life unified? All in one place and never lost again? Like the Sorting Hat, it may *look* like a small, unassuming item... but don't be fooled. It's one of the more powerful magical items out there.
Also, please do not bring close to the fire, as there is fear of modification.
I left my last one too near the stove, and it turned into a newt;-)