The chances of finding a beta key, let's say that 250 people log on to the server that you are on during your playtime, then using the commonly accepted assumption that 1 key drops every hour, 250/3=83, but let's assume that only about 150 of those players were able to get any real playtime in, which makes the odds of getting a key approximately 1/50 for one server.
However, I don't know the odds of Silver Freeze OUTSIDE of Smasho, but if anyone does know, just multiply that by 1/50.