i just got home from a couples massage with mr. mush. i thought alot about this thread while draping the male client for face down work.
i realized that i "err" to the side of caution and anticipate that the size of what's covered is larger than what i might think might be there, so as not to 'bump' into any part that might just be there. ;-)
i also think that when draping with a sheet only, that i fold/bunch many layers over the gluteal fold, to access the sacroliliac joint and the total hip area, which might account for a 'breezy' feeling of space between you and the sheet.
that mt you mentioned salty, seems a little too manipulative rather than geniunely interested. i'd never put you on the dime for why your lady took the gift certificate. in my world, i allow transferable GC's because i want to get hands on any'body' who might be a source for repeat business or word of mouth referrals.