Amanita sponsus is the newly described species suggested by @alan_rockefeller on Mushroom Observer, and seems like a likely candidate. It's not in the iNaturalist database for species, so it wouldn't let me officially add the ID. It may be the same species, but an older specimen, than the other 2 Amanitas that were growing 2-3 feet away from it. http://www.amanitaceae.org/?Amanita+sponsus

Habitat: oak woodland
Substrate: duff
Cap: 9 cm w; 6mm thick context (white) + additional 3mm layer above comprised of the cap cuticle (very pale tan) + flattened white remnants of universal veil (not sure if it was a splotch or if they were flattened warts that merged together - had a bumpy appearance); plane; margin not striate; faint chemical smell
Gills: white; adnexed
Stipe: 10 cm h comprised of a 5 cm h x 2.5 cm thick bulbous base, above the a 5 cm h x 1.27 cm thick compressed section, even; smooth; solid; pale greyish-brown over white, darkened with handling; annulus; cup was missing if there was one (this specimen had previously been picked up by someone else, examined, and set back down before we found it, so I don’t know if there was a cup and it went missing, or if there was never one) - As it was it seemed to have an indistinct volva, maybe no cup at all?
Spores: ? (waiting for spore print)