2009 Subaru Forester Oil Light

We were in an accident. Front and rear collision. It was with the repair shop for almost a month. We picked it up and while driving home, we had gone 52 miles the car started to decelerate we pulled it to the side of the road and it died. They towed it back to the collision center and then said it was out of oil. No oil light came on. No check engine light came on. They are saying that this was not caused by the collision but was just low on oil and is our fault.
Why would no lights come on to indicate a problem?