Welcome to the guest forums!
I'm sorry for your loss - losing property is never cool.
If a phone is stolen, the carrier will log the ESN as such and make that information available to other carriers, both major and minor ones. However, not all carriers check ESN when a customer activates a phone.
As for reporting an activation or attempted activation to a customer, I cannot speak for every carrier, but my assumption is that they would cooperate with authorities regarding the stolen devices.
I recommend that you call your carrier and ask their specific policy regarding recovered equipment, as it will vary from carrier to carrier.
Thanks for asking!