Garden Pests and Diseases: small holes in raised garden bed, 2 by Red1776head

Red1776head wrote:
Getting ready to plant winter veggies and noticed an infestation of Japanese beetle grubs...100\'s of them! EWE.
So I got some grub treatment that is good for veggie gardens and non toxic.
First I turned the soil to see if there was a critter hiding under the small holes...nothing.
I applied the treatment to the nicely leveled soil and watered well.
The next AM went to the greenhouse and yep, more small holes. It looks like a very small animal is digging from the top. Looking for grubs???
Anyway we set a couple of small mouse traps to see if we can figure out who/what is digging in the garden...no foot prints or tracks either.
I also found what looks like very very small droppings (third pic) as small as a grain of sand.
Anyone got any info?