Thanks, now I understand what you mean. Practically speaking, the linear fit line doesn't go through the points of the last 3 days at all, so it's not a valid fit for the population at all, so R^2 is 0.
I hope you would agree that trying to fit a time trend with 3 days of data is pointless.
Another thing to keep in mind, is that we didn't see VINs below the trend in the last 3 days could be because there were no certain color/wheel combinations with lower VINs in the last 3 days, and future color/wheel rotation could trigger a bunch of lower VINs being assigned.
Sounds reasonable but looking in the past shouldn't we have seen than a similar pattern?!