Is there a hidden trash can I can empty? I keep deleting things and clearing cache to try and clean up space on my android and it seems I just keep losing memory, as if it's all going to some huge trash bin and still taking up space. Is there a way to find and empty this trash?
To answer this question I'll need to get you to understand what deleting means. 


  Deleting is basically telling the operating system, I'm done with this
  storage space, give it to someone else.


Think of it like a room where an app comes with his stuff then if it so happens that the app gets uninstalled, they leave the room there. So when android is installing the next app, it comes takes up the room. Just because the app was uninstalled doesn't mean the room was also demolished.

This would also explain why it's possible to recover data(through third party apps) even after having 'deleted' it. Now Android and I should believe all mobile phone operating systems don't have a native way of getting this data back. By native I mean you can't recover data by using the OS like the way you can use recycler bin in windows. This is due to the fact that memory is a very very precious asset on phones (it's very limited and the OS would rather have it stored for some other reason) and having a recycler bin would simply end up taking  crucial memory making it more expensive to manage the phone.

So no, android doesn't have a recycler bin; but that doesn't mean you can't recover data. As to what might be taking up your memory consider wiping caches of your apps. 


  Cache is app data used on the go that is stored temporarily


.  Also some apps have a nasty habit of leaving behind files after being deleted. They do this in anticipation that you might install the app again and if so you can just come back from where you picked off. I would recommend clean master app from the google playstore as I've I'm used it before and it works superbly fine in determining which apps you don't need and finding out whether your storage is being misappropriated and by who. They also fully uninstall apps and bloatware not leaving any files behind.