transfers in would not have a zap receipt. zap requests are only created from nostr clients and zap receipts should be broadcasted from your LNURL service provider upon successful payment of the zap request. if you've changed your lightning address in the past, it's possible the zaps are going to your old lightning address. this happens if your old lightning address is on relays out there or cached on nostr clients. someone built a tool that can check relays for your outdated profile recently. i forget who made it though.