Hey, my rear mirror fell off..won't go back on, is there a special glue i need or

Nightmare,not sure if its the same now but i had a Ford Escort years ago and the mirror fell off, i got the sticky pads from Halfords put them on with hairdryer so glue stuck,the mirror never stuck properly and kept coming off i eneded up buying a rubber suction type i somehow can see this being a good look on Audi,i would go back to the dealer.
 
Had the same in my A3, went to local windscreen place and they gave me a few pads, told me wot to do, and it stayed on till i sold it..