I wouldn't call it a tsunami but it was a wind surge i guess. When i was young i would visit my cousin for a week or so who lived in a small area off of Bay Shore rd in Oregon almost to the end. There was a lighthouse out in the bay quite a ways but easily seen from the end of his street at the bay. One day the wind was blowing so hard the water was gone. We started walking toward the lighthouse not knowing how stupid an idea that was. Luckily his dad was suspicious of our activity and found us before the wind stopped blowing. I suspect the activity looked much like the diagram you posted.
I know exactly where that is and yes you certainly could have been a victim if the wind had quit or more likely switched direction possibly only a few degrees.
When I was little a cousin of my Dad would invite us to spend the weekend at their cottage at Quanicassee on the southeast side of Saginaw Bay. One summer the water was already low and this particular day the water was blowing 'out' even more...
maybe it was the same day and wind you experienced in Oregon...
A bunch of us 'cousins' started walking out to see how far the water had blown...
we were passing little pools of water where fish were concentrated...
Finally one of the adults figured out what we were up to and that we had gone 'far enough' and made us head back to shore.