You can have much more control if you want to. Monero gives the possibility to create multiple accounts, each containing multiple subaddresses, useful if you want to control multiple accounts. For example, you may want to have an @account for receiving donations and another one for your daily use. That will allow you to easily monitor incoming funds to your 'donations' account, without mixing it with your primary account.
You probably didn't. It's very hard to simply 'lose' your coins, since they are technically nowhere. Your coins 'live' on the blockchain and are linked to your account through a system of public and private keys secured by cryptography. That's why if you don't see your funds, it's probably because of a technical issue. Take a look at the 'Resources & Help' section at the top of this page for a list of useful resources that will help you identify and fix your problem.
