Can anyone tell me what this pipe is? Is something supposed to be connected to it? 2007 Toyota Prius.
That looks like the combustion air intake, and it's missing the final piece (callout 17752) that points the intake backward so it's not a ram intake for road gunk. You might decide the missing piece isn't super critical. It's $42 list price (less at discount) if you want to complete the picture.
Most likely it was removed to allow replacing the passenger side headlight bulb. With that piece installed, it's almost impossible to get a hand back there.