Scotty A4

Hi there was just wondering if anyone out there might have some advice for me about my Audi. I was just driving along as normal going down a hill in fact as I got close to the junction I clicked the gears into “N” and coasted down the slope but as I got closer to the junction I could see that there was no traffic so I clicked back into “D”. That’s when things went wrong I heard a small clunk and totally lost all drive in every gear including reverse. I had to get my car recovered from that junction back to my home. Does anyone know what it could be or can give me some advice as to what I need to do with it. The obvious stuff like fluid levels etc have been checked and are all ok. So I am at a loss as to what it could be and don’t fancy sending it to a garage to get told this and that has gone and it will cost ££££££££ to repair. Any advice would be appreciated. Thank you.