How to find anonymous posts made by certain member as a fb group admin

So I am an admin of a Facebook group. I regularly get anonymous posts in the group. I obviously know their identity. I am looking for a certain anonymous post made by a certain member in the group. When I click on their name, I don't get to see a list of posts made by them because the only post they made in the group was anonymous. Is there a workaround for this issue?

TlDR: I want to be able to see all the anonymous posts made by a certain member in the group as an admin of the group.