I'm not convinced that WDFW can issue a ticket for a federal requirement as well. The regs don't say it has to be attached to the license.
Here is the actual law, no mention of the federal stamp. For the record, I already have mine for this year but here is the law.
RCW 77.32.350
Migratory birds—Supplemental permit—Fees.
In addition to a small game hunting license, a supplemental permit is required to hunt for migratory birds.
A migratory bird permit is required for all persons sixteen years of age or older to hunt migratory birds. The fee for the permit for hunters is fifteen dollars for residents and nonresidents.

1- There is no requirement the stamp be affixed to your license.
2- WA is one of a few states that has not adopted the duck stamp requirement into their state codes. So what this means is you can't receive a state ticket in WA for hunting without a federal duck stamp, HOWEVER you will receive a federal ticket for hunting without the federal duck stamp. If you're contacted by a WDFW Officer hunting without a duck stamp he will record your information, write a report, and forward it to a USFWS Officer. The USFWS Officer will mail you a federal ticket via the mail. Why WDFW hasn't been like other states and simply adopt the duck stamp requirement into state code is beyond me.
