It may sadden you, but the patent was invalidated based on at least two pieces of prior art (patents in this case) that were both stick shaped dog toys.
The first is a patent (4577219) filed in 1984 for a stick shaped chewable dog toy ( http://www.google.com/patents?id=ANQ9AAAAEBAJ&printsec=a... )
The second is a design patent (D428220) filed in 1999 for a stick shaped pet toy ( http://www.google.com/patents?id=JJMEAAAAEBAJ&printsec=a... ).
If you were also curious about the gory details of its re-examination process, you can pull it off of the patent application information retrieval (PAIR) service ( http://portal.uspto.gov/external/portal/pair ) -- enter the reexamination request number off of the re-exam certificate ( 90/006301 ) and click on "image file wrapper" and then you can see all of the actions undertaken.