Dealership error on 320i

[Olivia]

I have 2 BMWs, an 88 e30 and my 320i, I do all the maintenance on the e30 but with the 320i I take it to the dealership, I took it in Monday for an oil change that took them 6 hours, I left without issue, then by Thursday my car alerted me to there being barely the min oil in my car, I was conveniently 5 minutes from the dealership so I dropped it off pretty !Removed!. I knew something was wrong when I noticed it struggling performance wise and then it alerted me. My concern is the likely hood of damage this may of caused and who’s going to pay for that. My other concern is what type of damage could I be looking at, I’ll be honest I can understand the basics but anything extensive imma be a fish out of water. The car measures the oil with the computer and I ran that measurement a few times in disbelief, it doesn’t come with a dipstick but the dealership checked it with a dipstick they had (apparently) and confirmed it literally almost didn’t have anything. I can’t imagine a dealership forgetting to put oil back into a car, they have it today and haven’t called me to explain what happened, they only gave me theories such as oh they may of not filled it up all the way or they may of left something loose and it leaked out.