HCK recalls when they found Z's remains.
"Extracts from H.C. Kimball's Journal," Times and Seasons 6, no. 2 (February 1, 1845):788
On Tuesday the 3rd, we went up, several of us, with Joseph Smith jr. to the top of a mound on the bank of the Illinois river, which was several hundred feet above the river, and from the summit of which we had a pleasant view of the surrounding country: we could overlook the tops of the trees on to the meadow or prairie on each side the river as far as our eyes could extend , which was one of the most pleasant scenes I ever beheld. On the top of this mound there was the appearance of three altars, which had been built of stone, one above another, according to the ancient order; and the ground was strewn over with human bones. This caused in us very peculiar feelings, to see the bones of our fellow creatures scattered in this manner, who had been slain in ages past. We felt prompted to dig down into the mound, and sending for a shovel and a hoe, we proceeded to move away the earth. At about one foot deep we discovered the skeleton of a man, almost entire; and between two of his ribs we found an Indian arrow, which had evidently been the cause of his death. We took the leg and thigh bones and carried them along with us to Clay county. All four appeared sound. Elder B. Young has yet the arrow in his possession. It is a common thing to find bones thus drenching upon the earth in this country. The same day, we pursued our journey. —While on our way we felt anxious to know who the person was who had been killed by that arrow. It was made known to Joseph that he. had been an officer who fell in battle, in the last destruction among the Lamanites, and his name was Zelph. This caused us to rejoice much, to think that God was so mindful of us - as to show these things to his servant. Brother Joseph had enquired of the Lord and it was made known in a vision.