Just keep the stuff and get it to another location. Like some of the other guys have said, dont keep it at your own place.
Worst case scenario: they know that it's AAS and know you signed for it.
However, even if they know this, they need to have the actual drugs to make a case. They can show all the test results etc that they want to a judge, and show the fact that you signed for the package, but if they cannot display the actual drugs themselves as evidence then you CANNOT be convicted for posession/importation of a controlled substance.
THis is the reason that when raids occur they typically occur almost immediately after the drugs have been delivered to the premises. THe police know that if the drugs arent there when they raid the premises then they have zero case. One of the basic evidential requirments of the posession/importation charge is that the police can display the said substance as evidence in court.
I've seen it happen. I've known people who have imported controlled substances. The police evidently knew fully well that there was a controlled substance in the package but they were slow to raid the premises and the substance had already left the property. So...no drugs = no evidence = no case.
If you ever accept a package with AAS or any other controlled substance in it, then make sure you have a way to get it out of the premises almost immediatley.
Bottom line: no drugs in your posession = no case....regardless of whether they know you signed for it.
fortunately, I do not live in the U.S (or australia for that matter) and so dont have to worry about being arrested for AAS.
Just get the drugs to a safe place ASAP and you're golden.