... and all I got was this lousy T-shirt

To be honest, it is not a lousy T-shirt at all, it is great T-shirt from the Linux Foundation actually. It has a simplified Tux icon and a little riddle on its front:

Warning: don't scroll down if you want to solve the riddle by your own. Scroll down in order to see how I solved the riddle.
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   2nd WARNING
   DON'T SCROLL DOWN IF YOU WANT TO SOLVE IT BY YOUR OWN !!!
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   Last WARNING
   Ok, either you have solved the riddly by your own or you are simply too curious ;-)
   OK, FEEL FREE TO SCROLL DOWN IF YOU WANT TO SEE THE SOLUTION !!!
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Actually, I was wondering whether I can solve the riddle by using the NumericalChameleon (yeah, you know I am the author of it, don't you?) and I am glad to announce that it can be used to solve the riddle as well. I entered the bitstream at the category "Positional Notations, Radix 2-36", and converted the value to hex. Since the Unicode character set is a superset of ASCII, and numbers 0 - 127 have the same meaning in ASCII as they have in the Unicode character set, it was possible to prefix each hex number by 00 in order to satisfy the expected input format at the "Unicode® Characters (Basic Multilingual Plane)" category. Below you see screenshots of both the NumericalChameleon (with the solution) and a hex editor in the background (with the solution) in order to verify the result.