Other than tracking transactions and seeing if when he "arrived" at team it was "assignment by NHL team" or checking capgeek.com for all 30 teams and correlating "non-NHL roster players" with the corresponding AHL roster with European loans?
(I can tell you that ECHL SF has one Carolina and two SJ players on their roster.)
The majority of the teams have an affiliation with an NHL/AHL team. But any NHL team can assign a contracted player to any ECHL team. Example the Komets are affiliated with the Ducks and Norfolk of the AHL but we have Kenny Reiter who is property of the Islanders and was reassigned by Bridgeport.