It's possible. Elements of DH Hill's Division were bivouacked at the Mumma Farm on the evening of Sept, 16th and a number of war memoirs have stated that rations were not delivered to those Hill brigades on that day. The commanding office of the First North Carolina Infantry Regiment (Ripley's Brigade) reported, for example, that his men received no rations and instead "feasted" on roasted corn and pumpkins that night. Those edibles were presumably gathered from local farm fields, which would have included nearby Miller's Cornfield. The officer did not specifically identify the source of the corn and pumpkins, however, so additional research is needed.
It's also worth noting that any number of Confederate units had moved close by Miller's Cornfield in the two or three days before the battle, so there was ample opportunity for soldiers to have pilfered any edible corn at that time.