Our bus from LAX was not the one with the character "wrap" either. Just plain white. Looked pretty much like the faker bus! Except when I flashed my voucher he was happy to have us on board, unlike the faker guy.
I saw that small shuttle too with disneyland express on it...sneaky sneaky!
But now you're aware of the sneakiness, and you'll get the voucher, at least for your trip from the airport. (you save a buck or to that way, too)
I think that one person from the Dis was taken by the faker, and had to pay far more for the ride. They didn't have the prepaid voucher printout, which as I've mentioned, worked like garlic on vampires, LOL.