It definitely doesn't hurt to ask, or even try.
Last time I was in L.A. I was able to use my UO Annual Pass to get a discount at a store at USH. The cashier thought "Two Park" meant USF and USH, but even when I explained that it meant USF and IOA he still rang up the discount without a problem. Anyway, the moral of the story is, it doesn't hurt to ask, since it would probably just take a nice Universal employee to make it happen.
I would suggest contacting Universal Orlando and asking them if there's anyway to change the park on the ticket (they do this when somebody accidentally buys a USF ticket and intended to go to IOA). If that doesn't work, then contact Universal Hollywood and ask, "pretty please", if they will take a Universal Orlando ticket, (don't let on that you already spoke to Orlando). As a last resort, I would recommend just showing up to the park that day and playing the part of the confused tourist who didn't know better ("Oh, I didn't realize we couldn't do this when we bought them." "I thought they told me we could use them at all Universal parks" and even "I can us Disney World tickets at
Disneyland").
Universal Hollywood is in real bad shape right now, and they've been offering all sorts of discounts and deals, like "Buy a one day ticket, get the rest of the year free! so I think they would rather make a guest happy then turn them away.
Good luck.
-Kevin