I don't know of many home owners who don't cash security deposit checks as there's always the possibility that if they need to charge it for some damage, etc it might bounce! This has been known on occasion so most take the precaution of cashing the check. So what your home owner does is perfectly normal practice.

Personally, I don't take a security deposit, just credit card info which is run for authorization purposes only, to ensure that it's a valid card, and no money is taken at that time. It's only in the case of damage or loss that we would charge it with the appropriate amount.

Each home owner has different methods which you should check out before you make your booking so that you're fully aware of what is going to happen, if it hasn't already been explained to you.

You can see from some of the replies above to your question about mailing a check has shown that some of the home owners didn't realise about the postage charge increasing. I'm betting that this has happened to your owner also. Cancelling the original check will have also cost your home owner money.