It would have been better if the police had only sent the three radios with the thief because then there would be less ground for the defendant to claim entrapment.
Entrapment occurs, as the link below says,when government officials do something
that induces a person to commit a crime he or she is not previously disposed to commit.
One can argue that the defendant was previously disposed to commit the crime of buying the three stolen radios, but that he was not disposed to buy the other 11 that the police sent along with the thief. Therefore, by sending the extra radios, the police actually bolster the defendant's ability to claim entrapment.
The defendant can also claim that the other 11 radios were not actually stolen property. He can say that, once the police got possession of those radios, the radios ceased to be stolen property.
It is not clear that either of these defenses will work, but they were made much more feasible by the police action in adding the 11 other stolen radios to the original 3 the defendant was going to buy.