This post reminds me that at the time of the purchase, BK also purchased the knife sharpener from Amazon. There was a post way back with a photo of it. The sharpener was never found. I wonder if when BK took that long ride to Costco, Kate's Cup of Joe, Albertson's, etc., that he didn't give it a toss in the river to join the knife and whatever else he may have tossed. (But I always thought he buried his kill kit in order to have his trophies close by).
And this reminds me, what WAS it he bought at Albertson's? Just wondering...
According to
this court doc, BK shopped at Albertsons the same day of the murders (November 13, 2022) for only seven minutes before checking out at the self checkout:
BK apparently did his regularly shopping (for food or women, who’s to say) at the 24-hour WinCo in Moscow. The closest Albertson’s to Pullman, WA is the one in Lewiston, Idaho, a 42-minute drive from BK’s apartment in Pullman. There are no Albertson’s near BK’s hometown in Pennsylvania.
According to the same court doc, BK tried to shop at Costco first, but he left immediately, probably because he didn’t have a membership card. He then drove past a Walmart store before moving on to Albertson’s.
All this is to say that I think BK wanted to buy something to eat instead of something to destroy evidence with, and I doubt BK was super-familiar with the Albertson’s grocery store layout.
He likely grabbed a piece of fruit and some nuts in the produce department near the store entrance, a drink from the nearby refrigerated section, then checked out.

Produce section of the Albertson’s in Clarkston, WA (
Source)
So, then, why on earth would BK drive 46 minutes south from his Pullman apartment to Clarkston to buy lunch at a grocery store (where he could use the self-checkout to avoid drawing attention to himself)?
Well, the address of the Albertson’s in Clarkston is 400
Bridge Street. Unsurprisingly, this street turns into a bridge over the part of the Snake River that flows north and forms part of the boundary between Washington and Idaho.
Bridge Street (highlighted in yellow) joins Clarkston with Lewiston, ID, which during the plea hearing Bill Thompson called the port city of Idaho since it’s positioned at the confluence of the Snake River and Idaho’s Clearwater River:

Source: Apple Maps
As first hypothesized on Jan 7, 2023 by
@Elliemay, and discussed on WS quite a bit afterwards by
@10ofRods,
@iamshadow21,
@DisplacedDivaofthe6C, and others, I think BK may have been scouting for places to dump his knife in the Snake River.
He needed daylight for that.
Now,
if the Azget Industries video shared earlier by
@MassGuy (and by another WS before an approved media source referenced it) is correct about BK burying his kill kit in a pre-dug hole off Sand Road just over the state line in Washington immediately after the murders while his phone was still turned off,
then here’s the path BK
may have driven from 1122 King Road to the pre-dug hole (note that the route takes so long because it is the
walking path generated by Google maps to the burial site, following drivable roads—otherwise, Google generates a shorter route that includes a highway, which the State thinks BK avoided since his car was not captured on camera there):

Source: Google Maps.
The red pin in the map above marks the location of the possible pre-dug hole, which you can see here (note the road pullout and stand of trees):

Source: Google Maps
Later that same day, according to the
Probable Cause Affidavit, BK’s phone utilized cellular resources that cover Johnson, WA (the PCA incorrectly states that the city is in ID, which doesn’t exist) from 5:32 pm to 5:36 pm:

Note that it was dark by 4:50 pm that day, and that Johnson is a short drive south of Pullman:

Source: Apple Maps
According to the PCA, BK’s phone then stopped reporting to the network from around 5:36 pm to 8:30 pm.
Interestingly, it is another short drive from Johnson to the possible burial site of BK’s kill kit:

Source: Google Maps
So it’s possible that BK temporarily stashed his kill kit in a pre-dug hole in the early morning darkness (immediately after the murders while his phone was turned off), then,
after darkness returned late the same afternoon, BK turned his phone off once again, retrieved his kill kit, drove
back to the Clarkston-Lewiston area and threw his kill kit into the Snake or Clearwater River. He had three bridges to pick from:

Source: Apple Maps
Now, if we think that BK safely buried his kill kit in that pre-dug hole in Washington, why speculate that he later
unburied it and threw it in a river? Well, Bill Thompson
did discuss the Snake and Clearwater Rivers during the plea hearing, and he also said
they never found the murder weapon. I’m pretty confident LE used metal detectors and cadaver dogs to check out the potential burial site discussed in the video and shown in this post, and any other plausible burial sites, but came up empty.
(Speculation)