I live alone, so no one else has used my computer.
I have approximately 5000 photographs stored in iPhoto.
On several previous occasions, I discovered a number of photos in Trash on the left sidebar of iPhoto. The number seems like it was the same, about 693 photos, or so.
In the past, one gentleman told me that I could open the Trash, select all, and then select a command (I don't recall the specific command, maybe "Undo") to return the photos to where they normally live. I did not find that command, but found another, "Put Back", which worked to restore the photos to where they normally lived.
That same gentleman also told me how to delete photos from albums, using "Command + Delete". This worked for awhile, and then several days ago, it stopped working. Tried "Control + Command + Delete", and it did not work either.
This morning, I successfully deleted one photo in an album using "Command + Delete". However, that did not work for the next, or any other, photos.
That same gentleman told me that I should not let the Trash get too full, as iPhoto does not "like" that. Therefore, I try to empty my trash basket on a regular basis.
This morning, after noticing another 673 photos in the Trash located on the iPhoto sidebar, I opened it, selected all, and hit the "Put Back" button. All photos seemingly were restored to where they are supposed to be.
I then closed out of iPhoto, and was getting ready to quit my session when I noticed the the trash basket icon in the tool tray at the bottom of my screen appeared to have trash in it. When I opened it, there was a "folder" in it that was named "iPhoto". At that point I looked to see if there was any "undo" command, and did not see one. That is when I asked for help, and got all of your clever banter.
Hopefully, this will provide you with enough information to develop some idea as to what is going on, what I am doing that results in unintentionally dumping things in the trash.