Have you checked the oil filter itself? On rare occasions I have seen the rubber seal partially detach when it is screwed on too tight or if there is debris or some of the seal from the last filter left on there. The seams could be leaking on it too. Just a guess. You also should have an oil cooler with a line to it but that is further back.

1997 T-100 4X4 Xcab,Warn Hubs
02 Camry LE
2008 Yaris