It's not there either. I think mass delete does not go to any trash.
Has the size of your iPhoto Library changed? Where is the iPhoto Library stored? On an external disk or on your system drive, and if external, how is the drive mounted? If you delete from iPhoto and empty iPhoto's Trash the photos will go to the system Trash, unless the library is on an external drive, that is remotely mounted.
Another reason might be, if you imported the photos referenced, that is, when the original image files are not stored inside the iPhoto library, but iPhoto is referencing them in their original location outside the library. You are importing referenced, if disabled the iPhoto Preference "Importing. Copy items to the iPhoto Library". In that case the originals of your missing events will be still exactly where they have been, when you imported them to iPhoto.