Originally Posted by
nacho
The problem is OP handed the key over voluntarily to the valet.
I'm pretty sure that Hertz permits valets to drive its cars -- at least in the U.S. See Post 2 in this thread:
Is Valet parking a breach of rental contract?
Edited to add: It looks like Hertz may have changed its authorized-driver terms since the time of that old FT post. See
nacho's post, immediately below.