The first thing you should do is stop using the memory card you used to take your pictures. The more you write data to it, the harder it will be to retrieve old data from it. Unless you used some sort of secure delete program, chances are very high that your pictures are still on your camera's memory card, even if they don't show up in the Finder and the card appears to be blank. When you ask where your photos are, I'm going to assume you mean the ones from the camera memory card, and not prior pictures you already had stored on your internal (or external) hard drive. I very highly recommend a free program named PhotoRec,
http://www.cgsecurity.org/wiki/PhotoRec. It is a program that will run through Terminal and goes after the data on a given disk, regardless of format. I successfully used it to retrieve photos from a friend's daughter's high school graduation earlier this year from an SD card that had been accidentally wiped. I also found pictures dated from a year ago during the retrieval process. So trust me, chances are good that your photos are still there.
What I did, and what I would recommend you do, is create a disk image copy of your memory card using Disk Utility in OS X. Then run the PhotoRec program on the newly created disk image. That way, if something goes wrong, you won't hurt your original data source and you can try again if you need to. The PhotoRec program will not put any watermarks on anything and is actually capable of retrieving other filetypes (such as audio) as well as image files. I accidentally deleted some audio files on a 1GB digital voice recorder last year and I was able to retrieve them all using this software.
I could type up a detailed step-by-step process, but this post is probably already long enough already 🙂. Give it a shot and see what you can do and let us know how it goes.