it might of got intercepted. They can't do anything to you unless they actually catch you holding the envolope, and then opening it. they can only catch you red handed, when its in your possesion. Otherwise, while its floating around the postal system, its in no ones possesion. You may get a letter from customs or some other simular body saying they intercepted it. But, as you said its under someone elses name, i really wouldnt worry. I wouldnt worry any way. They have much bigger fish to fry than to try a get you for sending a couple of grams in the post. You never know, it may just be lost, and may soon find its way through! (fingers crossed!)
I know I would.