Iphone, Itouch & Imessaging- Security issue

Heres my issue. My son had an Itouch. I then got him an Iphone, which in time caused me to repo the itouch. The itouch & the iphone get all his i messages (which is fine for me). Occasionally on the itouch I will turn off the imeessage for his number on the iphone, & when I turn it back on he gets a message on his iphone saying "dads itouch enabled", or something like that, & his phone can either accept it or not. However, I cannot find ANYWHERE, whether it be on his phone or his account saying that "Dads Itouch" is getting his imessages. Surely to god there should be somewhere he could look on his phone or his apple account that he could tell "dads itouch" is getting his imessages.

Is there anywhere?