srievley,
Check the link below for the Washington schematic.
http://www.cbtricks.com/radios/uniden/washington_mb8719/graphics/uniden_washington_mb8719_sch.pdf
There are times that manufacturers add a component to the solder side of a PCB. By studying the attached (if your Washington has an 8719 PLL) you may find that the diode should indeed be in the circuit.
If you have the 858 PLL in your Washington, the schematic can be located by looking at similar radios to your Washington. (i.e. Cobra 138XLR/139XLR, Palomar SSB500, President Adams, Grant, Madison, Realistic TRC449, TRC457, TRC458, Robyn SB510D/520D) Some of these schematics are on this forum. These "similar" radios may not be identical to your Washington, but similar enough to find the diode you see in yours.
Recently
Ez2cDave posted some copies of the Master Mods books (and
KlondikeMike cleaned them up!
Many thanks to both!) In browsing through them, I saw that there are instructions for installing the "Super Talk" modules in some of them. Volume 3 lists the Washington install. Perhaps "reverse engineering" the "Super Talk" install may reveal that the diode was added as part of this "Super Talk Module".
(Search under the topic "CB Manuals or Schematics" for the Master Mods books. I can't remember at the moment where they are parked.)
There is no greater satisfaction than solving your own problem. Maybe the information above will help you do that. If not, post your findings and there are many on this forum willing to help.
73's
David