How strange that you should ask at this juncture. I got a tip from Nanette on this forum a few weeks ago. She put me in touch with Phil, a resident of Wrightwood, who had recently stumbled across a backpack in the Acorn Canyon area. Phil described the backpack to me, and it really sounded like the my father's. It took us a few weeks to get our schedules to match. We actually got together
just yesterday. We went to the location, found the backpack, and, sure enough, it was my dad's. It had about the contents that I expected although it did not contain his backpacking stove which puzzled me a bit, but perhaps he had brought food that did not need preparation. We opened briefly my dad's bear cansister, but closed it due to a
particularly malodorous stench. I haven't had the courage (stupidity?)

to examine the food inside yet due to the truly foul smell emanating from the canister. The food has been in there since Jan 2004 (yipes).
All of the equipment is pretty much ruined after 3.5+ years in the wild, but it feels strangely good to have tied up this one last loose end in the saga of my dad's disappearance and death. I can't explain to you why, but I feel a sense of relief at having found the backpack.
There was one water bottle that was more or less intact, albeit smelly, that I may try to sanitize and use. It's kind of funny, but I have an odd sense that I keep a bit of my dad with me whenever I use some of his old equipment on a hike or backpack. Call it a memento or something I guess.
Thank you, thank you, thank you to those of you that have helped out or encouraged me in some way: Jon, Clint, Chris, Robert, Wrightwood, K9luvr (and probably a couple of others who my poor memory doesn't permit me to recognize here). Special thanks to Nanette, Phil, and Blake who directly contributed to the finding of the backpack.
Lastly, thank you all to the people who keep this forum going.
There is absolutely no way I would have ever found that backpack without you, the members of this forum. This forum, and the town of Wrightwood in particular, will always have a special place in my heart, despite the tragic loss of my own father. It is people like you who turn tragic memories into good ones. I thank you.