I deleted unwanted photos from my iPhoto library, emptied iPhoto trash & Finder trash... this did not free up disk space. please help!

Question

I deleted unwanted photos from my iPhoto library, emptied iPhoto trash & Finder trash... this did not free up disk space. please help!
I have a 15-inch MacBook Pro (Late 2011) with OS X Mavericks 10.9.5
Last week, my 500 GB Harddrive had 120 GB free space. I was feeling crumby and decided to make productive use of taking a day off to lounge around. I snuggled up with my laptop and dedicated hours to meticulously combing through my iPhoto Library. I had 13,000 pictures, and I got rid of those I didn't want. Having said "sayōnara" to about 6,500 pictures, I then emptied the iPhoto trash and the Finder trash. I took delight in the iconic paper crumpling sound of them vanishing into the digital void.
Everything seemed perfect: the photos I loved were still there, the photos I loathed were gone, both trashes were beautifully empty. Having thrown away all of those awful, boring, and unflattering images of poorly light lunches and selfies gone wrong, my iPhoto library was half the size as before! I felt renewed, a little lighter, somehow more free, and I expected my hard drive to be a bit different to.
I eagerly checked my storage stats. My heart sank to see that my 120 GB of free space, was still only 120 GB of free space. I restarted my MacBook; this did not help. I restarted it the next day; this also did not help. It's been 5 days and the hard drive still has 120 GB free space. This is not an emergency and it will probably be a good while before I clutter my laptop to the brim. Yet while I am glad I don't have to see cringeworthy pictures of my ex's unmentionables every time I'm showing off things I do want to remember, I'm still disappointed and now obsessed with solving this mystery.
What is going on? I don't see them, so where are they hiding? How do I get the free space I should have earned from throwing away 1,000's of photos?!

Answer 1

Thank you, Terence!
Yes, I only emptied the trash when it was really full, once I waited until the trash cans contained 2,600 photos and then I emptied them - Oooops! In the future, I'll keep in mind your suggestion of deleting less than 100 photos at a time.
I downloaded the iPhoto Library Manager and used it to rebuild my iPhoto. After a few hours of rebuilding, it generated a new copy of my iPhoto Library. This versions was nearly identical to the original (it was missing 5 photos and was therefore only 5 mb smaller). I guess my Library wasn't defective.
I checked my storage stats, and interestingly, using iPhoto Library Manager did help with the problem that developed after I re-indexed my hard drive. My hard drive is able to properly recognize data categories again, instead of listing almost everything as "Other". Understandably, my free disk space changed from 120 GB to about 60 GB, because my hard drive now contained a second copy of my iPhoto Library as well as iPhoto Library Manager. It seemed like all I needed to do was throw these away, but when I emptied the trash, my problem was not solved. My Hard drive now looked like this:
It appears to me that when I empty the trash, the things I throw away are just hanging around as backups instead of leaving! I went into System Preferences and turned of my time machine OFF. Now my hard drive looks likes this:
The back ups of the iPhoto files, and the program which I deleted, are still on my hard drive some where but now they are listed as "Other" instead of "Backups". Do you know where they might be and how I can delete them for good?