Sorry I’m just reading this because the valet (hotel) switch was the first thing that crossed my mind when I started reading the original post.
To others, yes, there’s a valet/hotel switch that will lock out the trunk. BMW usually puts in in either the glovebox or center console (whichever one that can be locked with the metal keyblade inside the remote fob). This allows you to secure items in the trunk when handing off your remote to a valet. They can’t use the remote fob, the interior trunk release or exterior trunk release…and can’t access the switch since it is locked and you have the metal keyblade with you.
The valet/hotel switch is
S5 in the illustration below (for the F06/f12/f13):
