Cortinarius

Cortinarius never grows on wood, for it is not capable of breaking down lignine nor (hemi)cellulose. They are mycorrhizal fungi, having an intimate relationship with woody plants. Lastly there is no sign of a cortina present, nor are the gills dark coloured, which are crucial identification marks for this genus. You indeed have an Oyster (Pleurotus spec) or maybe an Hypsizygus species. Based on the gills, which are free of the stem or very narrowly adnate, I'd suggest the latter one is the most probable choice. Both genera are wood decomposers.

Not an oyster mushroom. Looks like it may be a species of Cortinarius.