Help with trim ID

Hello all of you fine fellow Prius gen 2 folks - can anyone help me ID this plastic cover I just found floating around in my engine bay? I've never seen it before, it was hanging precariously kind of near the oil stick.

It might very well be a water pump cover or something to that effect - I've not gotten out the creeper and slid underneath to see if anything looks obvious - I'm not much of a contortionist so my first instinct was just to photo and ask.

It might even be a piece of road fodder that somehow magically got kicked up and through enough to stick, but I doubt it. Have definitely never seen it before.

Any help appreciated - thanks in advance

 

I had it in to have the shock mount replaced a couple of weeks ago - process of elimination seems to leave me with that thing being the cover to one of the new or old shock mounts, and it was left accidentally in the engine bay when the hood was closed. Glad it didn't jack anything up and bop around while in there! Lucky that it wedged itself in a harmless position.