Lechem Mishnah: Non-Kosher Roll

Can a non-kosher roll be used to take the place as the second roll for lechem mishna that you don’t eat?
I had a situation like that this Shabbos. It was Shalashudes and I realized we had only one challah. I knocked on the door of the nearest Jewish neighbor to ask if I could borrow a roll not to eat, but to take the place of a second challah. This neighbor does not keep kosher, but understands the concept. They gave me a roll that came from a kosher style deli in the area that has no supervision.