yep it's possible. it appears he was looking in the wrong spot.
blowing up the tree didn't help.
It's obvious to me, If he carved a Cross in the tree it was already Grown.
he would not have been able to dig under the roots to bury the money, unless he had dynamite too
the roots may have covered it in 30 years time, but there was no roots there when he dug. the tree may have been narrower too
the spot I would have chose would have been
the closest soft ground. then dug there and widened my hole
as I dug down. but not make noise or risk destroying the cache.