I have given up on Hertz at BOI for this very reason. The last time I tried for retroactive credit (#1 Gold Points, at that), I recevied this response:

"033 Only rentals taking place at participating locations in the U.S., Canada, Puerto Rico or the U.S.V.I are eligible to receive #1 Awards Points"

The sad part is, Hertz has by far the best selection at BOI. National (my other membership) has the usual crappy GM and Kia loss leaders, and has managed to place their return lane at the farthest possible point from the terminal, a good 100 yards across an open parking lot from the nearest door. But I suppose at BOI, none of this matters, as twice this year I have flown in on two days notice and found NO CARS availible from ANY agency, even off-airport. A couple of days riding in clapped out Crown Vic taxis and you'll take what they give you, points be dammned.