An AR15/AR10 will fit very nicely inside a guitar case, with room left over for ammo, handgun, etc. Would hotel staff think anything of somebody carrying a guitar case in a hotel that's going to host a music festival?
Or, how about a golf bag? I could get several rifles in a golf bag. Plus, the AR type rifle can be reduced in size by half, easily.
Multiple trips of someone ferrying in their own bags would certainly have been noticed by those who make their living from tips from carrying those bags.
I wonder if the investigation will be thorough enough to look into this detail by interviewing bellhops and video, or if it will just be accepted “as is”. Time will tell.