So when I drove PA 26 between Everett and PA 913 last night, I noticed that there was no signage for PA 915 TRUCK.
As a result, I emailed District 9 this afternoon about this, and I was told that the route never existed because the Traffic Unit considered it as unnecessary resulting in this route being entirely created due to a press release error that has not been fixed.
Anyway, this route will obviously be deleted after only being in the HB for a month.
EDIT: https://github.com/TravelMapping/HighwayData/pull/5791