That's why I always ask the teller to stamp received when I bank
in cheques, because if they lose the cheque, they can deny
responsibility.
I will only put cheques in quick deposit box if I am sure I can get
a replacement cheque easily.
What if one day, some crazy guy pours kerosene or methylated spirit
into the quick deposit box and set it on fire. Though the guy will
be caught, you might not be able to find a replacement cheque.