Money frozen in my account for no reason

A friend of mine transferred me money from his account because he didn't have money on him, I was in the que at the ATM and about to deposit money in my account. I told him he could transfer the money into my account and I would give him cash, I did this because the que was too long anyway. A day later the funds disappeared from my bank account, I made a bank statement and still didn't get clarity as to where my money went. I woke up in the morning and reported to the bank, they told me the funds were frozen because the money was part of a transfer ****. I don't know how because he transferred the money into my account and I gave him cash which I was gonna deposit anyway. They gave me this incident number *** and said I should provide an affidavit saying exactly how I received this money. They also said I must also get proof of payment from the guy and a copy of my ID and "maybe" they will return my money. I don't understand why I should jump into hoola hoops for my money in my account but I will do it anyway as it is part of my rent money, hopefully they will unfreeze it in time, I was supposed to pay rent today.