Yes, perhaps as it’s such a large area they do see it as a second home so feel completely comfortable leaving a separate hoard, Lilly no doubt thought you’d cleared it away when she gave you a little nip or maybe she was thinking hey, pass that on to Clive 
or perhaps she simply thought come on mum, refill the dig box, let’s get busy hamstering 
or perhaps she simply thought come on mum, refill the dig box, let’s get busy hamstering 
I also have white substrate scattered about and have made a mess in our home too 
