Hi, I have good experience in Asterisk, I've read your issue and I can say that there is no place in Asterisk or DB to see the wrong password of rejected peers, BUT, potentially, it could be possible to see it over the network dump (of course if the traffic is not encrypted);
As far as I know, you can see only the hash, but not the password,
anyway, you can check your network dump and maybe you will be lucky :)
If you want, you can drop a message, but I've already described here all the issues of your project;