They may wonder at the size of the nut horde we planned to bury.
speaking of huge holes: Chile’s Chuquicamata Mine (largest open pit mine - (world’s largest hole and second largest orange hole)) is easily recognizable from space… and given its environment, will be there for thousands or hundred-of-thousands of years - prob. only to be mitigated by seismic activity
I think you’re underestimating the number of days.
For example, last year, we had a very mild January and February, where the temps were hovering around 0C for two months.
That meant thaw-freeze cycles every day and night.
It’s not just a couple of days in the spring and fall; goes on throughout the winter.
There’s a reason all of our houses have basements: it’s to get below the frost line, or else the house would collapse.
Pompei is a special case, it was immediately covered by a thick layer of ash. So perhaps it’s a good example of the case of “holes and tunnels filled in” level of archeological preservation. There’s an exposed section of brick wall near the tower of London that was the original Roman wall _ buried until recently. Hadrian’s wall is still visible, but as a pile of grass-covered rubble. The Great Wall of China is kind of an anomaly, various sections are 600AD, most of the good parts are about 1300AD and under constant repair for tourists. (I have a picture somewhere I took of some fellow repairing some of the steps ( “Government project - 600 years and still under construction…”)
Which leads to the question:
Was @Lumpy thinking the squirrels would be wondering about how vast a number of ordinary sized nuts would fit in that hole?
Or instead that the squirrels would think a hole of that size was needed for just one of our Nuts of Unusual Size? N.O.U.S.? 
It might be taken as evidence supporting a revival of the “mesas are the stumps of giant trees” theory. 
Must… control… myself… to avoid political jabs in this forum.