ATM did not give me all of my money?

I went to the ATM to request 120 from the ATM machine. It's was a gas station ATM I know I should have never used it, but I needed some cash before work. Everything was good until the cash started dispensing. It only gave me $20.00 then this error came up on the screen and a receipt printed saying that there was an error C0056 and says partial reversal. Now when I checked my account the full $120 has been deducted. I called my bank and they told me I had to wait a full 7 days before I could complain and I should try contacting the bank of the ATM Machine which I cannot get a hold of because the ATM machine prints out the number to the gas station. I brought it to the cashier's attention and he tells me that it will probably be returned to me within 24 to 48 hours. Does this happen all the time? When will I get my money back?