sapling oak tree

My husband grew an oak from an acorn and when he died in February we dug it up as it would have been too big for our garden and transplanted it into the church yard. We have been watering it regularly and it has withstood some terrific winds, however the small leaves which only started to appear in June now have gone brown and died. I will be heart broken if the tree is dying, is there anything we need to do. It is about 5ft high and the diameter is about 4 inches. We have laid bark around the bottom to retain the moisture.