I'm feeling your pain.
New idea:
Print up that picture in the form of a flyer and post it at your local upper end sporting shops (a huge portion of Whitney hikers come from socal). Add some sort of firehouse logo to the flyer if you can, so to appeal to the humanity of a person if he/she did find your flag. Almost everyone who hikes Whitney stops at the REI, A-16, and the local shops in Lone Pine. Give the Portal Store a call and ask them to post one in both the store and the Hostel (the hostel number is listed on the portal store forum + address to send flyer)
Finally, People are grubs for T-shirts and if I recall, every station/company has its own logo shirt. Offer a firehouse T-shirt as a reward.
I hope this helps.
