All US states and territories have unclaimed property laws. Some have escheat laws. The former means that the unclaimed property is forwarded to the state treasurer (or other similar official) who holds it for some period of time. In other states, the funds are escheated which means that they become the property of the state.

Take a look at the URL. If the URL is a delta.com location and you are not being asked to confirm any information beyond yes or no, you are likely fine. If not and it turns out to be real and you let the funds sit on the card, they will be paid to the Washington Treasurer and you will need to reclaim from that official.