Does this small piece of code seem ok?

With a random 16  alphanumeric string, I don't even check if it is duplicated. The chances are too low. If you're still worried increase the string length.

Just because the changes are low does not mean you should ignore the fact it CAN and at some point WILL happen. You can't cover every single scenario in programming, but to ignore something like this that is quite easy to avoid is just bad practice. But that is my opinion