Do you have a filter set on the Trash?
Check the Search Field in the Browser, if it is set to "Showing All" or something different.
Unrated or better may be hiding "rejected" images.
If your search filter is cleared, but you still do not see any images, check for an invisible filter - see Frank Caggiano's User Tip:
However, please note that the correct command is not "Hold the option and command keys down while starting Aperture."
Both ways will work. Frank's answer is perfectly o.k., if you want to troubleshoot your current Aperture Library - the library you last used. Holding down the ⌥⌘-key combination while double-clicking the Aperture icon in the Dock or the Applications folder will launch into the Aperture Library First Aid dialogue, like this:
And why should we assume, that your Trash problem is with an Aperture Library different from the one you last opened?