Man, this problem comes up a lot.
First, you can open a case with Nortel and they can access your system remotely and reset it for you, but be warned, it is costly (and should be).
Second, if you really can't get a hold of the past technician, you will have to do a level 2 reset which will set everything back to default values. You won't lose your keycodes per se, but you will have to access KRS ad pull them down and reload them. Yes, you will have to reprogram everything from scratch as well, including your voicemail, AA, CCR trees etc etc. You will also need to have all the latest patches put back in too.
If this isn't reason enough for people to remember to just write down their passwords, I don't know what it's going to take. We get one of these emails at least once a month on this site alone but I guess some people just won't learn.
Third, and this is a stretch, if you were set up with an account (and you know what it is) that has administrative privileges, you can reset the master password that way.
Good Luck,