It wasn't a partial mash, it wasn't a mash at all, because there was no malt containing enzymes, unless you have left some details out. Mashing is holding a base malt and water at the right temperature for the enzymes to convert starch to sugar. Unmalted grain can go in with the malt in small portions and it will also be converted. Steeping is a homebrew technique where ingredients which have already been processed so that they are made up of soluble sugar, like crystal malt, or have been essentially burnt in roasting so they no longer contain starch and protein and just add color and roast flavor, like black malt, are soaked in water. They give up some of their sugar and color flavor to the water before the boil. Soaking raw (unmalted) grain in water as you apparently did just makes starchy water. Some brewing ingredients simply aren't suitable for extract or even partial mash brewing, and flaked oats is one.
Hope your head stops spinning. (When it does, you might start working g through a good book like Palmer's How to Brew. Until.then, remember the mantra, RDWHAHB: relax, don't worry, have a homebrew.)