Chicken egg thief?

[Yesterday I found a chickens egg in the lawn buried by a tree. It looked like there was a little hole made for it and it had been revealed by strimming the grass in that area.]

Didn’t know trees buried eggs Scarlet.
Any further forward with the mystery?

If it's  a squirrel, fox or a tree burying these eggs, where are they getting them from?

There are chickens two fields over from me. All I can assume is a Fox is stealing eggs and bringing them here to hide. Lots of foxes here now. I gave up chicken keeping because I couldn't keep them out.