Today I was observing WhatsApp app behavior. 

By using camera I took a photo. That photo got stored in camera directory of my cell phone (obviously that is normal behavior). And after that I shared the same photo to one of my contacts using WhatsApp. After sharing, I deleted that photo from camera directory and checked my WhatsApp contact (to whom I shared the photo) it was still in the list of messages.

Then I found over the Google that WhatsApp also stores sent images in internal directory as well. Then I deleted the same photo from WhatsApp internal memory and checked WhatsApp contact (to whom I shared photo), I found that there was not real photo but blurry image of the same photo was there (that is called thumbnail). 

I tried to find out from where it was getting that thumbnail? I searched my whole cell phone directory or even WhatsApp media directory as well but could not find the thumbnail. My question is what is the location in cell where WhatsApp stores the thumbnails? I am assuming that WhatsApp keeps thumbnail url and download on demand. Is that right? Any help?