When you loses wallet, it has the effect of removing money out of circulation. Lost bitcoins still remain in the block chain just like any other bitcoins. However, lost bitcoins remain dormant forever because there is no way for anybody to find the private key(s) that would allow them to be spent again. Because of the law of supply and demand, when fewer bitcoins are available, the ones that are left will be in higher demand and increase in value to compensate.
Your claims are true, when the wallet or private key got lost, it will never be recovered and will be lost forever unless it will be cracked by someone or something. These lost coins contribute to the scarcity build up in Bitcoin which contribute to the increase in Bitcoin's price.