The identifying information that's included in Silent Posts (x_cust_id, x_subscription_id, etc) should always be in webhook transactions, if not just everything in Silent Posts. I know about refId but that's of no use to companies using ARB for recurring billing, which is 99% of our transactions.
This is making my migration to Webhooks difficult. Your support staff has obviously been instructed to push everyone to webhooks if they're using Silent Post right now but the glaring omissions of functionality in webhooks is just absurd.
The only solution is to query the Authnet API for information on the transaction ("getTransactionDetailsRequest"). The response that comes back from that query is very detailed. That detailed response should just be webhook. Why the heck not? Come on now.