Considering that nearly all gun transfers between non-FFLs including loans of muzzle loading rifles made after 1898 are required to cross an FFLs books and thus be entered into Washington's data base your point is moot here. However, if the LEO looks to anti gun local bureaucrats for promotions it may prompt the LEO to scavenge for barley justifiable reasons to confiscate any guns that they find. For example, the Mason Count Sheriff has been quoted in the Mason County Journal stating that they confiscate all guns from all residences in which they handle a domestic dispute. Seattle's behavior has had to be corrected by the courts a few times.

Keep that in mind when Michael Bloomberg's group promotes a universal back ground check in your state.

Edit to add: I have found that the best approach to dealing with LEOs is keep it friendly and say something like I appreciate them checking on unfamiliar people moving around at odd hours. You could have to call on the same LEO for help someday.