Dealerships are not required to give anyone a loaner. It's a courtesy, nothing more.
I have come across some dealerships that only have loaners for those that bought a car from them. Again it's a courtesy.
2016 F82 M3: SO/SO • DCT • <Waiting for allocation>
2011 E92 M3: AW/BLK • DCT Europäische Lieferung am 6. August 2010