Oil Thermostat Gasket, what else could it be?

[MW3Designs]

Well, I set out on the mission to replace what I thought was the oil thermostat gasket leaking, but after getting everything apart I'm not sure of that is the issue. There is oil on the alternator and the vicinity, but when I got a look at the oil thermostat, it looks to have been replaced at some point, the part is shiny clean, and one of the e-torx bolts was replaced with a standard hex bolt. Ive only had the truck for a few years, so I don't know when or where it might have been done.



So my question is, what else could be leaking in that area? Here is a pic of the Oil Thermostat, the seal circled in yellow looks oil free, but the lines circled in red are wet with oil. Could it be whoever changed it didn’t put new o-rings on the lines and they are the culprit? In the second pic you can clearly see that one of the e-torx was replaced with a hex bolt, so I know for sure someone’s been here before.