Silent, because some things are absolutely clear. Sometimes the obvious need not be explained as such.
If anyone involved had any inkling that the 2nd Amendment was a "collective right", then there would be no question that Mr. Miller was NOT acting as a part of that collective. Mr. Miller was well-known to the prosecution and the courts as a habitual criminal offender, variously convicted of or suspected a party to bank robbery, murder, moonshine making, booze running, etc. - caught with the unregistered NFA item during alleged criminal activity, NOT anything anywhere remotely related to organized militia activity. Mr. Miller was plainly a thug with a gun, the furthest one could conceivably get from any arguably legitimate connection to a lawful collective to which a RKBA could conceivably be attributed. If any argument can be made for the "collective right" theory, it most assuredly and obviously did NOT apply to Mr. Miller.
Despite every level of government involved being keenly aware that Mr. Miller was utterly criminal in his occupation, and absolutely & plainly not a part of any legitimate "collective", how much time was spent discussing whether, gun aside, the 2nd Amendment applied to him personally? none. zero. zippo. nada. nyet.
Despite the court, being faced with a known violent habitual criminal offender, having plenty of reason to find any and all ways legally conceivable to deny this man any right to weapons of any kind, and the weapon in question being federally deemed dangerous enough to warrant (inflation adjusted) a $3000 tax on a $10 gun, did they in any way address the notion that somehow, in any way possible, the 2nd Amendment might not apply to this individual? cue the crickets - nobody questioned that Mr. Miller, legally vile to the extreme, had some sort of right to keep and bear arms.
The Miller Court never did say whether it was a collective right or an individual right - because it was inconceivable that the right could be "collective". Of course it was individual! Should the notion have had crossed the court's mind, or the prosecution's mind, it would not only have been addressed, it would have been the first thing used to deny Mr. Miller standing (contrast Parker, where the "standing" issue arose only as a vague side query by a judge, and in mere minutes grew such as to eject 5/6ths of the plaintiffs).
You're right: the Miller Court never did say whether it was a collective right or an individual right - any more than a modern discussion of geography debates whether the Earth is flat or round.
The case before the U.S. Supreme Court was whether or not the NFA was constitutional. Specifically, whether or not the tax stamp was an infringement under the second amendment.
The case had nothing to do with either a collective or individual right. Are you sure you even read it?