Where is the memory inside this RFID tag
The IC is likely underneath that plastic encapsulation. That black "blob" at the bottom right of your second picture.

The IC is probably much smaller than you are imagining. It's not going to be anything like an SOIC package that many picture a "digital IC" to be.

This method is used frequently in consumer electronics I've seen. TV remote controls coming to mind most quickly. You would need to peel back or scrape this layer to see the IC underneath.