It isn't uncommon for blacktails to 'wave the white flag' when they run away. They can look much like whitetails when they do this.
So - is there whitetails here? It is certainly possible. People transplant fish from waters to waters and I would not be surprised to hear of a whitetail enthusiast transplanting deer. I think western WA would be and area they would thrive in.
When I lived in SW OR in the 70s, I knew 2 old guys who were at the release sight just outside of Roseburg, OR when the whitetails were released. They told me there were two release sights. One just outside of Roseburg (I know the very spot) and one near the Columbia river (I don't know the exact spot of that one). Those old timers called them 'Mexican whitetails' because they came from down south near Mexico (otherwise known as cous whitetails these days). My how some stories have changed since then! Those 'Mexican whitetails' are extremely small and when I lived there, they were hated by all the locals and ranchers. Advance forward in time and - these days, guys will pay thousands of dollars to fill a tag for a breed they think is native to that area. If only they knew.....
I worked in a slaughter house back then and I can say for sure, even though they were protected, we had them come in occasionally. Those are some small deer! They also crossbreed with blacktails which is what the locals there didn't want to see. I saw many crossbreed bucks. The outcome is small too.