They were really popular in around 2007 or so when masses started buying them, just like the .co hype it quickly faded. You really get to see the true worth of a 3 'character' domain as alittle bit over exaggerated, but a 3 'letter' domain to be worth a resell price.
3 character domains (.i.e u9x.com) are really not worth its registration value unless it can be monetized because its using some sort of acronym.
3 letter domains are worth its weight. ABE.com, etc...
.coms are seen to be worth multi millions (sex.com) but averages a couple thousand.
3 number domains are worth a couple hundred to a few thousand.
.com has obviously more value than .net and .org seems to be lower valued than .net
A site with some reference to the current price in the market
Code:
http://www.3character.com/priceguide.html
I figure other than trying to find a acronym for the domain, it maybe just listed on an domain auction and you may get your money back.