My friend buyed Bitcoins in 2011 from Austrian Company, they make payment via Bank. After few months they lost his iPhone where is stored all data from company and Bitcoin account. From that time they is unable to find that company,
I do not know the situation in your country, but here you can request bank transaction data for a year back, and therefore you can ask the bank to send you the details of that transaction, and then you may know where you made the purchase.
I don't think there was an iPhone app that was in 2011, so most likely your friend used a web wallet.
Yes, you are right, they receive from that company wallet ID, and other creditials. They tell me also receive notifications from that company about BTC price changes.